OpenRouter Cost Audit: Billed Rates for 20 Image Models Diverge From Listed Prices by Up to 50%
In September 2026, OpenRouter ran a systematic cost audit of 20 commercially available image generation models, billing each through its API and recording what it actually charged rather than what was listed. The results expose a market where developer cost estimates routinely break against actual invoices.
What They Were Actually Billed
GPT-image-2 returned a 1024x1024 PNG for $0.006 — the lowest billed cost across all tested models. At the other end, Google’s Gemini 3 Pro Image billed $0.1344 for the same resolution, a 22x gap at the extremes.
| Model | Billed | Output | Billing Unit |
|---|---|---|---|
| OpenAI GPT-image-2 | $0.0060 | 1024x1024 PNG | token |
| FLUX.2-Klein-4B | $0.0140 | 1024x1024 JPEG | megapixel |
| Riverflow v2.5-Fast | $0.0176 | 1024x1024 WebP | image |
| FLUX.2-Pro | $0.0300 | 1024x1024 JPEG | megapixel |
| Qwen Image 3 | $0.0300 | 1024x1024 PNG | image |
| Krea 2 Medium | $0.0300 | 1024x1024 PNG | not published |
| GPT-image-1-mini | $0.0333 | 1024x1024 PNG | token |
| Gemini 3.1 Flash Lite Image | $0.0336 | 1024x1024 JPEG | token |
| Recraft v4.1 | $0.0350 | 1024x1024 WebP | image |
| Seedream 5.0 Lite | $0.0350 | 2048x2048 JPEG | image |
| MAI Image 2.5 | $0.0482 | 1024x1024 PNG | token |
| FLUX.2-Flex | $0.0500 | 1024x1024 JPEG | megapixel |
| Grok Imagine Quality | $0.0500 | 1024x1024 JPEG | image |
| Grok Imagine 2.0 | $0.0600 | 1024x1024 JPEG | image |
| Riverflow v2.5-Pro | $0.0641 | 1024x1024 WebP | image |
| Gemini 3.1 Flash Image | $0.0672 | 1024x1024 PNG | token |
| FLUX.2-Max | $0.0700 | 1024x1024 JPEG | megapixel |
| Recraft v4.1 Vector | $0.0800 | vector SVG | image |
| Seedream 5.0 Pro | $0.0900 | 2048x2048 JPEG | image |
| Gemini 3 Pro Image | $0.1344 | 1024x1024 PNG | token |
The Listed-vs-Billed Gap
The audit’s headline finding is not the absolute prices but the divergence between what providers list and what they charge. Sourceful’s Riverflow v2.5-Pro listed $0.13 per image but billed $0.064 — exactly half. Black Forest Labs’ FLUX.2-Flex listed $0.06 per megapixel and billed $0.05. FLUX.2-Max, by contrast, listed $0.07 and billed $0.07 exactly.
Krea 2 Medium presented a different problem: no published pricing at all, but billed at $0.030 — in line with mid-table competitors, just undocumented before the transaction.
The discounts appear to come from caching, provider-level bulk agreements, and routing optimization rather than advertised rate cuts. For developers building cost models, the implication is that listed rates are a ceiling, not a floor, and actual spend may be substantially lower.
Billing Unit Diversity as a Trap
The audit surfaces a structural issue for developers estimating at scale: billing units are not standardized. Token-based models (OpenAI, Google, Microsoft) price based on image resolution — a switch from 1024x1024 to higher output will increase the bill proportionally. Megapixel billing (Black Forest Labs) normalizes to area in a similar way. Fixed-image billing (most other providers) charges the same regardless of output resolution at the tested size.
The practical trap: comparing GPT-image-2 at $0.006 against FLUX.2-Pro at $0.030 on a fixed-size request understates the gap when factoring in 2K or 4K outputs, where token-based billing scales up and fixed-image billing stays flat.
Resolution Arbitrage
ByteDance Seedream’s pricing strategy stands out. Seedream 5.0 Lite returned a 2048x2048 image — four times the pixel area of a standard 1024x1024 request — for $0.035, the same price as Recraft v4.1 at standard resolution. Seedream 5.0 Pro returned the same 2048x2048 output for $0.09. On a per-pixel basis, both Seedream tiers offer the highest resolution value in the tested set.
Recraft v4.1-Vector billed $0.08 for an SVG output — a format that scales to any resolution without quality loss — putting it in a different comparison class than raster-output competitors.
Bottom Line
The cheapest route for standard 1024x1024 raster output is GPT-image-2 at $0.006. FLUX.2-Klein-4B is the cheapest open-weight alternative at $0.014. For high-resolution needs, Seedream 5.0 Lite’s 2048x2048 at $0.035 is structurally cheaper than any token-billed model at equivalent output.
Listed prices should be treated as approximate. The audit found consistent discounts, with the largest divergence reaching 50% below the listed rate. Budget estimates built on provider marketing pages will overstate actual API spend.