How Much Do AI APIs Cost? 2026 Pricing Breakdown

By the Zylo team · Updated June 8, 2026 · 5 min read

The cost of using an AI API depends on three variables: which model you call, how many tokens you send as input, and how many tokens the model generates as output. There is no single AI API price — the market spans roughly three orders of magnitude between the cheapest open-weight models and the most capable frontier models. At the low end, GPT-OSS 120B costs $0.039 per million input tokens and $0.18 per million output tokens (as of June 2026). At the high end, GPT-5.5 costs $5 per million input tokens and $30 per million output tokens. The same 10-million-token workload can therefore cost anywhere from a few dollars to hundreds of dollars depending solely on the model choice. This range is not arbitrary: it reflects differences in model size, inference compute, and the capability level each model delivers. Before optimizing cost, it helps to understand the mechanics of token pricing; the guide on how tokens work covers the fundamentals, including the input-output asymmetry that often surprises new API users.

The full pricing spectrum

Zylo bills every model at its published base per-token rate with no per-token markup. As of June 2026, the catalogue includes models across every price tier. In the sub-dollar-per-million range: GPT-OSS 120B ($0.039 / $0.18), Gemini 2.5 Flash Lite ($0.10 / $0.40), and DeepSeek V4 Flash (about $0.10 / $0.20 input and output). In the mid-range: GPT-5.4 Mini ($0.75 / $4.50) and Claude Haiku 4.5 ($1 / $5). In the premium tier: Gemini 3.1 Pro ($2 / $12), Claude Opus 4.8 ($5 / $25), and GPT-5.5 ($5 / $30). The right choice depends on the task. Lightweight models handle classification, extraction, summarization, and simple question answering at a tiny fraction of the cost of a flagship. Flagship models justify their price when the task demands complex multi-step reasoning, nuanced writing, or deep code generation that smaller models cannot reliably complete. The Zylo model catalogue lists every available model with current rates so you can compare options before integrating.

Estimating a monthly bill

Estimating monthly API spend requires three inputs: average tokens per request (input plus output), requests per day, and the model’s per-million rates. Multiply tokens-per-request by daily requests to get daily token volume, multiply by 30 for monthly volume, then apply the rate. A document-processing pipeline that sends 1,500 input tokens and receives 500 output tokens per call, running 10,000 calls per day, generates 15 billion input tokens and 5 billion output tokens per month. At Claude Haiku 4.5 rates ($1 / $5 per million), that is $15,000 for input plus $25,000 for output — $40,000 per month. Switching to Gemini 2.5 Flash Lite ($0.10 / $0.40) reduces the same workload to $1,500 plus $2,000 — $3,500 per month. The Zylo pricing calculator handles this arithmetic interactively, letting you adjust request volume and model tier in real time. For a curated comparison of the lowest-cost options at each capability level, the cheapest AI API guide benchmarks the leading budget models against realistic tasks.

What drives your bill up or down

Two workloads on the same model can cost very differently, so it is worth knowing which levers actually move the number. Output length is the largest, because output tokens cost several times more than input and a model told to “explain in detail” can easily triple a bill that a concise instruction would have kept small. Prompt size is next: long system prompts, large few-shot examples, and full conversation histories are all input tokens you pay for on every call, so trimming them compounds across high volume. Model choice sits on top of both, since moving a routine task from a flagship to a lightweight model can cut its cost by ninety percent or more. Finally, repeated context — the same documents or instructions resent on each turn — is pure waste that caching or windowing removes. None of these require a new provider; they are prompt and routing decisions you control, and together they usually matter more to the final invoice than the headline rate of any single model.

Starting free and scaling gradually

Zylo offers a free Basic plan that requires no credit card and provides approximately 200,000 tokens and 7,200 requests per day on Basic-tier models. This is not a trial that expires — it is a standing tier designed for exploration, prototyping, and low-volume production use cases that fit within the daily limits. When usage grows beyond the Basic plan’s scope — either in volume, in model tier, or in request-per-minute requirements — paid plans (Go, Pro, Mega, Enterprise) add credits and higher rate limits. The API key itself is free on all plans; you pay for tokens consumed, not for the key or the account. A flat 25 percent platform fee applies only when you add credits to your account, never on usage. This means your per-token cost equals the published base rate exactly, and the only additional cost to plan for is the funding fee at top-up time. Starting on the Basic plan, profiling real token volumes with the calculator, and then choosing the paid plan tier that matches your workload is a reliable way to avoid both over-provisioning and surprise charges.