Drew, the most inexpensive paddle bags I know of aren't paddle bags,
they are gun socks or ski-snowboard bags.

You can pick up a Remington gunsock for less than $5 at Wally-mart. Ski
bags or snow board bags are a little trickier, but if you bide your
time you can usually find them on end-of-season clearance for $10 - $15.