Because the honest number depends on what you already have, and a price list would make us guess it. A store with photographed products and written copy is a different job from the same store without them — and a price list that covered both would have to quote the worse case to be safe.
So the price comes after one call, in writing, as a single figure for the whole job. Not an hourly rate, not a meter, and not a number that moves once you have agreed it. If the scope grows, the extra is quoted before it is built.
We also quote before we ask your budget. Most studios here ask first and price to it. You get our number, and then you decide.