I got a spam email from NewEgg the other day offering a 2GB SD card for under $10. It really amazes me just how cheap storage is these days, and how small it is getting. My first computer in 1994 cost me a little over $2000 (on an 18% interest credit card - thank you college credit card pimps). It had 4 MB of RAM and I think a 100MB hard drive. I had long since replaced it by the time I paid if off.
For some real nostalgia, take a look at what a gigabyte of storage use to look like and what it looks like now. My how the times are a changing.
Now, Western Digital has some new drives out. They have a relatively fast 1 TB drive (7200 RPM), but their speed crown goes to their 640GB 7200 RPM SATA drive. Now, imagine 640 of the devices you see above. Then imagine the cooling and power requirements for such a beast... and then the size of the mainframe that would be accessing such data.