I've noticed due to the worsening of the us economy that many pet stores have been closing down, and the owners sell off their wares for much less than retail.
Walmart has decent priced aquarium products, too bad I can't say the same for the livestock.
Check pet stores for bargain bins and discounted items.
If you don't mind buying used equipment you could find a diamond in the rough, I have bought used filters and all you really have to do is change the filter media and it is good as new.