I also don't think $30 is that much.
You didn't tell us if you want front and rear or just rear fender.
You also didn't tell us you already have fenders, and all you want is to extend the end of your current rear fender with something like that Rubber Mud Flap from VO. There are all sorts of ways you can do that cheaply, you cut up a milk bottle and attach it to the end of the fender. Just get creative if $30 is too much.
If by some chance your confused, which I doubt it, but if you are, and what you want is an actual fender and not an extender, then consider a product called the Ass Savers, they're around $20, they also make a mud guard if making one yourself doesn't appeal to you, it's called the Ass Savers Muddler, they're $10 less than the one your bike shop showed you.