Hard Drive Breakdown

Ok, so! I'm sure this has been asked 100 times and I did search around but I didn't find exactly what I was looking for. Here's what I did.

I tore down 20 hard drives and came up with these results:

1. HDD Covers - 4.4LBS (Steel, I think?)
2. Magnets - 2.12LBS
3. HDD Boards - 1.3LBS
4. Aluminum Rings(washers to get to the platters) / HDD Motors - 1LB
5. HDD Actuator Arms - 12OZ
6. Misc Connectors (they connect to the actuator arms) 2.4OZ
7. Platters - 2LBS
8. HDD Aluminum Casing - 10LBS

All in all, after a ton of research here and on eBay I totaled around $68.50.

I'm just looking for clarification in terms of pricing, what goes for what, and if I'm breaking them down properly. Any advice would be greatly appreciated!