I looked at going that way when I first started a couple of years ago. I had a LOT of hard drives, and as you , expended a large amount of time and energy getting them out. The trouble is, they are never JUST the ringht shape or size, and finding a lot the same is difficult too. The older chunky looking HDs, the ones that look the size of a lunchbox, have some very nice ones in, but I think finding those is rare
I came to the conclusion that hard drive magnets make very good magnets for hard drives, and saved myself a lot of headaches by buying some nice neos. I know that people have used them, but it just wasn't for me.
The ones I did recover are now used for holding notes to a glass window partition in the office (the glass has that chicken wire reinforcing in it).