Inexpensive degaussers or HDD shredders?

I could have sworn this has been asked before, but I can't find a close duplicate...

With only 10 disks to get rid of, you should do what I do: take the covers off and take the voice coil magnets out. They're rare earth magnets and some of them are quite large, they make great fridge magnets, and are useful for lots of other things.

If you want to be very, very sure no-one could get the data off, the first thing to do is to wipe the voice coil magnet over the surface of the platter you can see, which will mess up the servo tracks, making it essentially impossible to recover the disk. (I have one magnet from an old DEC 1GB drive that is 1cm thick and can wipe a hard drive without taking the cover off.)

I usually stop at getting the voice coil magnets out, but for an HR machine I once took the platters out and broke them and disposed of half of the pieces at work, half at home.

We use an inexpensive drill press. One or two passes and the platter is done.

Thermite (be careful)

If the drives aren't capable of being wiped with software, mechanical destruction of the platter is about your only option (Good news! It's usually the fun way as well!).

If you don't have a lot of devices to get rid of, you can try using thermite which is typically fairly inexpensive to obtain (depending on where you live) and is completely irreversible (some military aircraft use thermite to destroy stored records in flight computers if the aircraft crashes in a foreign country). Take the top cover off of the first drive to make sure you're placing the thermite so that it melts through as much of the platter as possible.

A less fun but equally destructive method is to remove the individual platters and run the surface of them randomly across a bench grinder. You can probably borrow or rent one for a couple of hours and not have to spend much money compared to buying a degausser.