I just bought 2.5 terabytes of hot-swappable SATA-300 storage for $730. If I count only the cost of the 500-GB hard drives at $120 each, I'm getting 4166 MB of storage for every dollar. Fifteen years ago, I got 0.4 MB for every dollar and that's not even adjusted to inflation. That's more than 10,000 times the storage for the same dollar, not adjusted for inflation.
Here are the five 500-GB Seagate hard drives with the hot-swap drive cage.
See George Ou's blog
for more details.