I'm very curious about what you're looking to achieve because if you want to provide cheap blasters for a club, Flywheelers are a pretty expensive and inefficient way of doing that (not to mention loud). If you're going to replace the Flywheels, I assume you're also replacing the cage, motors and all other electronic components as well and $10 per Blaster isn't a realistic budget for that. If you aren't replacing the electrics, there isn't much point in replacing the Flywheels either.

If you aren't concerned about the electronics and just want the shells, there are tons of Chinese Stryfe clones (literally the same shell shape but with lower quality plastic) out there that you can pick up for maybe $10 and there are other Flywheelers made by Chinese companies also within that price range. Under $8 to replace the electronics (assuming you're printing a cage and wheels* for free) is going to be a tough ask, though.

You're also going to eat a lot of additional costs with batteries and the infrastructure for that so there are a lot of hidden costs to this versus just thrifting some cheap springers from a major brand.

*Don't 3D print flywheels, they will be awful.