340 Lifter Clacking.... Reasonable Price?

I've never heard of the magnet method...... Anyone else tried this? Seems like it would have to be a pretty hefty magnet, unlike the WalMart brands....

AND, the tranny shop DID indeed take it out, for the "test-drives", BUT the lifter was clacking when I took it in.............I also limited my throttle before I took it to the shop so they couldn't hammer it.