Hidden costs of AI assistants: credits, overages and call minutes
By 3Gen editorial team. Every term below was read on the vendor’s own page.
The headline price is the number on the pricing card. The real price includes what happens when you run out, what the add-ons cost, when a discount ends, and how many seats you are forced to buy. None of these are secret. They are just in the FAQ, a footnote or a second tab. We collected them here.
If you want a credit-priced assistant with few surprises, OpenAssistant is worth considering. When you run out of credits its page lists three options (wait, upgrade or buy a top-up from $15) and no overage rate, credits you buy never expire, and built-in recurring tasks such as Daily Agendas and End-of-Day Wraps do not use credits on paid plans. Town and Lindy publish lower prices per credit at larger sizes.
1. Credits that run out, and what happens next
| Product | When you run out | Do unused credits roll over? | Source |
|---|---|---|---|
| OpenAssistant (ours) | Wait for the next cycle, upgrade, or buy a top-up (from $15) | Plan credits: no. Purchased credits: never expire | openassistant.us |
| Town | Free and Starter: prompted to upgrade. Pro and up: overage at $0.030 to $0.044 a credit, but only if you raise the overage cap, which defaults to $0 | Not stated | town.com |
| Lindy | “Lindy pauses and tells you.” Top-ups are $10 per 1,000 credits | Monthly credits: no. Top-up credits: kept until used | lindy.ai |
| Claude (paid plans) | Wait for the 5-hour or weekly reset, upgrade, or turn on usage credits billed “at standard API rates” | Not applicable | claude.com |
| ChatGPT Pro | Included usage first, then your credit balance, for eligible features | Not stated | OpenAI help |
| The X Subscription | Top-ups, or wait for the weekly refresh | Not applicable | x.ai |
| Gemini (Google AI plans) | Limits refresh every 5 hours up to a weekly limit; you can buy AI credits to extend | Not stated | gemini.google |
What to watch: a credit allowance that resets monthly is “use it or lose it.” If you buy a big tier for a busy month, the leftover does not carry over. OpenAssistant’s purchased credits and Lindy’s top-up credits are the exceptions in this list: they do not expire.
2. Overage rates
Town is the clearest example of published overage pricing:
| Town plan | Included credits | Overage per credit | 1,000 extra credits cost |
|---|---|---|---|
| Pro | 5,000 | $0.044 | $44 |
| Power | 12,000 | $0.038 | $38 |
| Power Plus | 40,000 | $0.032 | $32 |
| Team (per seat, pooled) | 6,000 | $0.038 | $38 |
| Team Plus (per seat, pooled) | 18,000 | $0.030 | $30 |
Source: town.com/pricing. Math: 1,000 × the per-credit rate.
Compare that with the plan’s own rate. Town Pro’s included credits work out to $0.0118 each on monthly billing ($59 ÷ 5,000). Overage at $0.044 is about 3.7 times that ($0.044 ÷ $0.0118). Running steady overage is the expensive way to buy credits; Town itself calls it “your upgrade signal.”
3. Third-party models and API usage billed on top
- The X Subscription: “Third Party model usage in Cursor is not included in the monthly prices shown and must be purchased separately,” at API list prices (x.ai/pricing).
- Claude Enterprise: $20 per seat per month “plus usage billed at API rates” (claude.com).
- Microsoft 365 business plans: “Some AI experiences require usage-based billing and may result in charges based on usage, beyond your license fees.” Copilot Chat is included at no extra cost for eligible plans, but “an Azure subscription is required to use agents and is priced on a metered basis” (Microsoft).
4. Call minutes and phone numbers
Voice products price each piece separately, so the per-minute headline is rarely the whole bill.
| Platform | Per minute | Also charged | Source |
|---|---|---|---|
| Retell AI | $0.07 to $0.31, by model and voice | $2 a month per phone number; 20 concurrent calls included, then $8 a month each; optional add-ons from $0.005 a minute | retellai.com |
| Vapi | $0.05 platform fee | Speech, model and carrier costs on top; extra concurrency $10 a line a month; HIPAA $2,000 a month | vapi.ai |
| Bland | $0.14 on Start | Telephony billed separately; call transfers $0.05 a minute on Start | bland.ai |
| Cal.ai | $0.29 | Requires Cal.com; individuals buy credits separately | cal.com/ai |
Example: on Retell, a build using a mid-priced model works out to $0.149 a minute ($0.055 voice infrastructure + $0.015 voice + $0.015 US telephony + $0.064 model). 500 minutes a month is 500 × $0.149 = $74.50. Add one Retell number ($2) and you are at $76.50, before any add-ons.
5. Add-ons that sound included
- Calendly: its AI assistant Callie and its Notetaker are an add-on bundle. Standard goes from $10 to $18 a seat a month on yearly billing (“Standard Plus”), and Teams from $16 to $24 (“Teams Plus”) (calendly.com).
- Pally: the free plan is free, but Cloud Mac is “a separate paid add-on” with no price shown (pally.com).
- Howie: a white-label assistant email at your domain is $20 a month extra (howie.com).
6. Introductory prices that expire
| Product | Offer | When it ends | Source |
|---|---|---|---|
| Microsoft 365 Copilot Business add-on | $18 instead of $21 per user per month (yearly) | First year only; offer runs July 1 to December 31, 2026 | Microsoft |
| Google Workspace | Up to 50% off for new customers | The plan cards say the discount runs 3 months; Google’s footnote limits the intro price to the first 20 users and says standard pricing applies after 12 months | workspace.google.com |
| Fyxer Pro and Team | “Unlimited credits” | First 3 months, then 3,000 (Pro) or 6,000 (Team, pooled) credits a month | fyxer.com |
| Otter Business, monthly | $24 instead of $30 | “20% off for 3 months+” | otter.ai |
Budget for the regular price, not the launch price.
7. Seat minimums
| Product | Minimum | What that means for a 1 to 2 person team | Source |
|---|---|---|---|
| Claude Enterprise | 20 seats | At least $4,800 a year in seats (20 × $20 × 12), plus usage | claude.com |
| Calendly Enterprise | 50 seats, from $15,000 a year | Not for small teams | calendly.com |
| ChatGPT Business | 2 users | A solo buyer can’t use Business; Plus or Pro instead | chatgpt.com |
| Claude Team | 2 seats (“teams of 2 to 150”) | Same | claude.com |
| Fathom Team and Business | 2 users | Same | fathom.ai |
8. Refund rules
- Town: “We don’t offer refunds.” You keep access to the end of the paid cycle (town.com).
- Skej: cancel early and “you will not receive a refund,” but paid features stay on to the end of the term (skej.com).
- Google AI plans: “No refunds for partial billing periods” (gemini.google).
- Microsoft 365 business plans: a 7-day cancellation window with a prorated refund after a paid subscription starts (Microsoft).
- OpenAssistant (ours): downgrades and cancellations apply at the end of the current billing period; plan credits are not refundable (openassistant.us).
An annual plan with no refunds is a 12-month commitment. See annual vs monthly billing for how many months you need to use a plan before annual pays off.
A checklist before you buy
- What happens at 100% of my allowance: stop, wait, or bill?
- Is there a spending cap, and is it on by default?
- Do credits roll over, and do top-ups expire?
- Which features cost extra (models, agents, phone numbers, add-ons)?
- Is today’s price introductory? When does it end?
- Is there a seat minimum?
- Can I get a refund if I cancel an annual plan early?
Related reading
- Usage-based vs flat-rate AI pricing: which is cheaper for you
- Annual vs monthly billing for AI assistants: what you save on each
- AI assistant cost for a 10-person company: per-seat prices
- OpenAssistant pricing: every plan, credit tier and price
- Free AI assistants in 2026: what each free tier gets you
FAQ
What are the hidden costs of AI assistants?
The main ones are credits that run out, overage rates, third-party model and API usage, call minutes and phone numbers, add-ons that sound included, introductory prices that expire, seat minimums and refund rules.
Do unused AI credits roll over?
It depends. OpenAssistant’s plan credits do not roll over but purchased credits never expire; Lindy’s monthly credits do not roll over but top-ups last until used.
How much is overage on Town?
$0.044 a credit on Pro, $0.038 on Power, $0.032 on Power Plus. Overage is off until you raise the cap, which defaults to $0.
Are there refunds on annual AI plans?
Often not. Town offers no refunds, Skej does not refund early cancellations, and Google AI plans give no refunds for partial billing periods. Microsoft 365 business plans have a 7-day window.
Which AI plans have seat minimums?
Claude Enterprise needs 20 seats, Calendly Enterprise 50, and ChatGPT Business, Claude Team and Fathom Team or Business need 2.
Try OpenAssistant
Want to start where there is nothing hidden to pay? Try OpenAssistant on the free Starter plan with no credit card, then see OpenAssistant pricing for the Pro plan, top-ups and billing rules. Or try Skej for scheduling.