I bought one for $50 around 18 months ago. I used it a lot when I was buying a house. It was a lot cheaper to scan and email than to pay for fax. I don't use it a lot anymore. If you buy one get one that doesn't need an external power supply.
We have a Canon MP250. It prints, scans, and copies. Was roughly $40. Works great and replacement ink is reasonable. Have scanned a lot of pictures and some papers too.
I wouldn't buy an individual scanner. Like BIM, I have a Canon, but a MX330. Prints, scans, faxes and copies. And it is basically free.
It's the razor-blade marketing model. Sell the unit for cheap and pay for the ink. I think mine was $70, but they are selling for $50 now. With 2 ink cartridges included you are basically paying for the ink and get the all-in-one for free.