Some pictures the studio can't make you.
The self-serve styles are flat and decorative on purpose — that is the kind of pattern that carries a working code without any fixing up. A photographic scene is a different job: most of the picture sits in mid-tones, which is exactly where a code stops being readable, so it takes hand work, several passes, and someone deciding when it is right.
Three cowboys riding through a saguaro desert under the Milky Way, with a payment code inside it, took about forty attempts and a repair pass. That is what this is for.
Why it is quoted and not listed
The price depends almost entirely on how hard your subject is to hold a code inside, and that is only knowable by trying it. A dense allover pattern is easy. A single portrait on a plain background is very hard. Quoting a flat rate would mean overcharging the easy jobs to cover the hard ones, so we would rather look first and tell you.