I worked in a legal firm which specialized in e-discovery and forensics, they weren't data-recovery specialists, but they were able to pull data from slack space and previously rewritten areas. But that is besides the point. For client-privacy reasons, legal reasons, and corporate policy, they ended up with hundreds of hard drives per month that needed to be destroyed with no possible way to recover the data. A $24 sledgehammer is certainly a cheap and fun sounding answer. But after smashing five hard drives, this stops being fun, you're making a lot of noise, and someone would need to clean up the mess. I'm sure OSHA wouldn't approve of that either. We were in a corporate office in the middle of New York City, so smart-ass solutions like thermite; sodium hydroxide; shooting them with a
.45, a shotgun, or a bazooka aren't going to fly. Because of chain of custody, you couldn't even take the hard disks into an empty field to do this.
The guy responsible for destruction started unscrewing everything, taking out the platters, then punching a hole in the platters with a screw-press. But like the sledgehammer solution, this was slow labor-intensive. I believe they ended up using a qualified HD destruction service, who would come to your office once a month, and give you metal confetti back. This of course isn't cheap. Eventually, purchasing one of these Garner devices would make economic sense.
My point is, sure, given our own devices, we can think of quick and fun ways to destroy a hard disk. But when you are limited by government and corporate rules, companies like Garner aren't just greedy, but filling a real need.