I've gotten sets buying complete boat packages at the right price. Then sell off the parts or boat package and keep what you want. (TRAX) and you'll end up getting them free or even making money off other parts. I've done this several times and eventually sold the used sets and ended up put it toward a new set for 550 (with shipping).
Can't build a set that works for less. You want them to float in water, and be light enough to carry. They hold their value well and last forever if you keep them out of the UV.