Automatically no 3d printed case is worth $300 because it's not possible to make it good enough quality.

A metal and wood case could be worth $300.

A good design is worth something, and a good printing job is worth something, and the convenience of a service is worth something, but no amount of good design and quality printing job and service convenience can make a 3d printed case worth more than about $50 before shipping, and it would need to be somehow pretty special design to overcome some basic material and process weaknesses and still be functional and look good to be worth that much.

$300 is too high, but $50 is too low. 3D print sellers aren't doing injection molded parts at scale, nor offshoring the labor. For GP's linked case file; between the filament, the compatible linked switch and fan hardware not purchased by the thousands, and someone paying themself at least minimum wage to print all 46 individual parts and then to partially assemble and package it up nicely (and not counting printer hardware depreciation or electricity), $50 for it is not a viable product to sell or to run as a business. That's the price I would budget for making it myself with the 3D printer I already own and not counting my time as a cost, not something I would waste my time with selling.

The cases are $60, the "original" price, not $300. Search ebay for BC-250, they're everywhere.