Buy the cheap fenders. I get most of mine from the dumpster.
Before west marine's "sale" those fenders were $75 each. CRAZY!!!
The only thing I'd check about your fenders is do they deflate. Some super cheap ones don't and that makes them harder to store when you're cruising and the ones I have seen that don't deflate die pretty quickly.
Cheap fenders are fine. Don't get ripped off just because it's "marine".