I notice that the QY300 is a sequencer, not a computer.

The key question: when the drive worked could it read floppy disks formatted for use in a personal computer?

If no, pay the $300.

If yes, and if you feel you'll be able to take it apart and get it back together, you've certainly got nothing to lose by replacing the floppy drive with one from a computer.

As for a drive for an Atari or "ammega" the same key question applies: when the drive worked could it read disks formatted for those computers?

Caveat: Replacing the drive won't work if the problem is with the drive controller rather than the drive itself.