To be fair, nerdy accessories and jewelry can sell in crazy amounts and for crazy high dollars, if it's done right.
Look up any collab with Square Enix for Final Fantasy XIV. Fender did a limited edition Stratocaster for the game that went for $3500 and sold out almost instantly.
In Japan, Citizen had a collab with them for watches that went for about $300 each after conversion. Again, they sold out quickly. If you want one now, you'll expect to pay anywhere between $400 and $600 if it's a complete set.
Depending on the game, you may run into a fanbase that's not just extensive, but also wealthy and willing to spend their wealth on merchandise for the game.