Thank you for the detailed response! I hadn't realised EOL parts were so cheap. 🙂
If we really want to talk about cheap stuff...
I have another HUGE pile of IDE/PATA drives lying around. Without counting, I'd guess that I probably have about 100 stashed here or there.
A lot of them are, again, pulls that I got for free(pulling them myself) and some are pretty low capacity(4-20gb). Even so, I find 80s and 120s fairly often. I like these capacities, as Macs made prior to 2002 don't natively support drives larger than 128gb at full capacity.
I've paid for bigger drives, although I did get a virtually new 500gb WD Black with a late 2011 manufacture date as a free pull(I think SMART showed it with about 200 power on hours).
Microcenter carries refurbs in 80, 160, and 250gb. They are a dollar or two more than refurb SATA drives of the same capacity, but even so 80gbs run about $6 each, 160s run $12-14(depending on brand-WDs are more than Seagates) and 250gbs are around $20. I never leave the store without buying a big stack.
All the above is true for 40 pin 3.5" drives. 44 pin 2.5" drives(laptop drives) are somewhat of a different story, and big capacities-especially at high rotational speeds-get really pricey even when well used. It's been a while since I've bought a platter 2.5" PATA drive. Instead, I buy mSATA SSDs, which run $40-50 each for 120gb or so. I then use enclosures that mimic the form factor of a 2.5" PATA drive. Not only are they cheaper, but also can saturate the ATA/100 bus in late model Powerbooks(I'm not aware of any platter drive that came) are silent(15" Powerbooks have the drive right under the trackpad, and 7200 rpm make uncomfortable vibrations. IMO, the make a great replacement, and I frequently get compliments on how fast and responsive my late-model Powerbooks are. About a month back, I used almost nothing but my last generation 1.67ghz 15" Powerbook for a week, and while it was slower than even a Core2Duo Macbook, it was still plenty fast for web browsing and other light uses.