I agree that it’s not worth trying to build a hundred-obsolete-drive array, but I strongly disagree with turning them into garbage prematurely. Sell or give away on ebay/craigslist/freecycle/whatever instead. There are lots of people who can make good use of a few end-of-life-but-still-working medium capacity drives. Just make sure you erase them thoroughly first. Realistically ‘dd if=/dev/zero of=/dev/sda’ is plenty; to be absolutely sure give them one pass with a fast random number generator first.

If you want magnets you can take them from failed drives.