AI billing: how to charge customers for AI usage

What are the ways to charge customers for AI usage?

There are five common methods. They differ in when you get paid and in who carries the cost when a customer uses more than expected. The examples come from vendor pricing pages. Prices checked November 10, 2026.

• AI agent pricing models compared
• Per-seat vs usage-based pricing

How do I work out what one unit of AI work costs me?

Add up every paid step in one unit of work. For an AI feature that is usually model tokens, paid tool or data calls, and the share of runs that fail and retry. Billing and card fees come off revenue later.

Example: a research task sends 20,000 input tokens and gets 2,000 output tokens back from Claude Sonnet 5.5. At $2 and $10 per million tokens, that is $0.04 plus $0.02. Three Brave web searches through Locus Pro add $0.0909, at 30.3 credits each. The task costs $0.1509. If 1 run in 10 fails and is retried, budget about $0.166 per finished task.

• Model tokens: input, output and cached input have separate prices. A Claude Sonnet 5.5 cache hit costs $0.10 per million tokens, against $2 for fresh input.
• Built-in tools: web search on the Claude API costs $10 per 1,000 searches plus tokens. OpenAI lists web search at the same $10 per 1,000 calls.
• Paid data APIs: search, scraping, enrichment and speech each have their own price per call.
• Failures: a run that times out still used tokens, unless your provider releases the charge.

• How to track LLM cost per user

How much markup do I need after fees?

Card fees take a fixed slice of every payment, so small payments cost more to collect. Stripe charges 2.9% plus 30 cents per successful card charge. On a $20 top-up that is $0.88, or 4.4% of revenue. On a $100 top-up it is $3.20, or 3.2%.

The table applies three markups to the $0.166 task above and subtracts a 4.4% card fee. Billing software adds its own fee on top: Stripe Billing takes 0.7% of billing volume on pay-as-you-go.

A 20% markup leaves little room for refunds, disputes and free trial usage. A flat fee per call or per task protects margin on very cheap calls.

Should customers prepay or pay after they use AI?

Ask self-serve and new customers to prepay. Usage stops when the balance runs out, so an unpaid bill cannot grow. You also hold the cash before your providers bill you.

Invoice in arrears for enterprise contracts that need purchase orders and monthly invoices. Then you need a meter, a credit limit and alerts.

Check how your billing tool enforces a balance. Stripe's basic billing credits apply only when an invoice finalizes, so a customer can spend past the balance during the cycle. Stripe's Metronome product burns credits down in real time.

• How prepaid credits work
• Stripe usage-based billing explained

How do I bill customers for AI tool calls with Locus Pro?

Locus Pro Enterprise gives each of your customers a credit balance. Your server names the customer on each call with the X-Locus-End-User header. Locus checks that balance before the call runs and returns HTTP 402 if it is short. Otherwise it charges the catalog base price plus your markup, and the markup is your margin. The ledger and customer analytics group every charge by customer.

Markup can be a percentage, up to 100% by default, a flat amount per call, or both. Example from the Locus catalog on November 10, 2026: Brave web search has a base price of 30.3 credits, or $0.0303. With 20% plus $0.002 flat, the customer pays $0.03836 and you keep $0.00806.

Customers fund their balance by card through Locus-hosted checkout or an in-app widget. Or you bill them your own way and move credits to them from your pool. Enterprise costs $200 a month with $30 of included credits and up to 240 tool calls a minute.

• Locus Pro for platforms
• Plans and prices
• Tool catalog

How do I choose a way to bill AI usage?

Match the billing unit to what the customer values and to how your cost moves. Then pick the tool that enforces it.

• AI cost per user is small and even: a seat price with a fair-use limit is simplest.
• Cost varies a lot between customers: prepaid credits, or a subscription with included usage and overage.
• The AI finishes a result the buyer already counts, such as a resolved ticket: price per outcome, high enough to cover failed attempts.
• You sell only your own product's usage: a billing engine such as Stripe Billing, Metronome or Orb is enough. Locus Pro bills only calls made through its catalog.
• Your customers' agents call third-party paid APIs: Locus Pro Enterprise supplies the APIs and bills each customer at base price plus your markup.

• Usage-based billing software compared