Then the way to go is to use Pareto frontier, e.g. https://quesma.com/benchmarks/binaryaudit/#cost

If you want to avoid using Opus 4.7 them why GPT-5.4 (unless with a disclaimer that it is low reasoning setting, or check that on medium its price is comparable with Haiku/Flash).

Also, usually it is good to look at the newest model. Gemini 2.5 Flash is quite dated. Gemini 3.1 Flash Lite is the new one (https://openrouter.ai/google/gemini-3.1-flash-lite-preview).