Are you saying for what you would charge in general if you were to make them, or this item in particular?
Depends on what people would want on it and how long it would take you. I'm assuming you'd have them send in the items to you and you wouldn't supply them. You'd have some competition as there a few established custom painters already doing this that do amazing work.
As for the OP item who knows. Its just pink... I dunno.
Heres a link to my custom painted NES, ive tried selling it but its tough.
"I virtually know nothing about the virtual boy"
SNES - 660