Here's why. These units not only use a very small 1 or 1.5 inch hard disk, but the drop could incur other damage. That's a reasonable estimate from what I've seen.
Bob
My son got an 30 GB Creative Nomad MP3 player for Christmas. He dropped it a couple of weeks ago while walking our dog. The device now is showing a HDD failure error.
I was wondering if I could go to an electronics parts store and get a replacement HDD.
The manufacturer said the repair would be around $100 to $150 -- seemed kind of pricey.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic