Lets talk materials...
$100 in glass and resin(cheap home depot resin and glass)
$100-300 in paint
and lets say $50 in cloth and MDF
oh I almost forgot about the bondo and primer add another $50.
So thats $400 just in materials and a so so paint job. Now add in a regular shop rate($60(which is cheap)) and assume the guy can haul ass and it only takes him 25 hours to build the box 60x$25=1500. Theres your $2k for a custom one off box. Thats not including a custom airbrush job, or multicolor paint. If you want something that nobody else has, its gonna cost you. If you want something made out of a mold its a lot cheaper.