The attempts multiplier dominates
Nobody accepts the first generation. A workflow that needs five attempts per usable image costs five times the price list, and the price list is what every budget is built on.
The effective cost per accepted image is the only figure worth quoting, and it is usually three to five times the headline.
Reducing attempts is the whole game
A more specific prompt, a fixed seed when iterating on one variable, and reference images all cut rejections. Prompt work pays back faster in image generation than anywhere else in AI tooling, because the multiplier is so large.
Wide aspect ratios need more attempts than square ones. Budget the allowance per ratio rather than as one average.