@LeviKornelsen It would depend on how likely I think "custom" means "more expensive" and how expensive the non-custom ones already are.
If I want the color of Set A used in the mold for Set B, is that any extra work or cost than just making Set B in its regular color? Do they normally make 20 sets at once so custom orders mean not making 19 matching sets at the same time?
I'm more likely to follow through if there's some indication of price: "Custom orders welcome (typically X%-Y% more)".