Originally Posted by notfred
Panniers ARE really expensive. People talk about commuting by bike to save money, and then they expect you to spend $200 on what is essentially a canvas bag, not all that different from a backpack you can get for $20.
Or you could get some cheap used ones on ebay.
You could sew your own. Ideas how by Ken Kifer:
http://www.kenkifer.com/bikepages/touring/bags.htm
Really it is nice to have your gear NOT sweating up your back all the time. (depending how much stuff you have and how far you are going)
Panniers are different than a backpack, they are designed to easily fit over the rack of the bicycle. They are cut away at the corners so you can clear the pannier with your foot when pedalling.
There are a lot of quality panniers much cheaper than $200, and a $20 backpack is sure to fall apart quicker than your quality panniers.