ChipFlip
Here's a comparison that only makes sense on the used market: 300GB for $100.00 against 3TB for $40.00. The WD VelociRaptor and the WD Caviar are both spinning 3.5-inch drives, and the smaller, more expensive one is the more interesting object.
The VelociRaptor was the fast option before SSDs existed
10,000 RPM against the Caviar's 5,400 or 7,200. In 2008 that made it the drive you bought for a boot volume, and it commanded a large premium for meaningfully lower access times.
Then SSDs arrived and made the entire premise obsolete. Any modern SATA SSD beats a VelociRaptor on every access-time metric by an enormous margin, silently, using a fraction of the power.
So why is it still $100
Collectors and retro builders. A period-correct high-end machine from that era wants the drive that was high-end then, and there aren't many left in working condition. That's the same dynamic that keeps limited-run cases and discontinued flagship GPUs expensive.
It is not priced on utility. Nobody is buying a 300GB 10K drive to actually store things.
The Caviar is the one that still has a job
3TB for $40 is genuinely useful as bulk storage: media libraries, backups, anything where capacity per dollar matters and access time doesn't. Spinning disks remain the cheapest way to hold a lot of data.
Check SMART hours and reallocated sectors before buying any used mechanical drive. They fail differently than SSDs, usually with warning if you're looking.
Bottom line
For storage, buy the Caviar. 3TB at $40 is real value and the VelociRaptor's speed advantage stopped mattering fifteen years ago. Only buy the VelociRaptor if you're building a period-correct machine, in which case you're a collector and you already knew that.