Here's the deal man: you're not gonna get a budget priced kegerator conversion kit. The parts just cost too much to begin with. $300 is pretty good for 3 kegs, in fact, i would go ahead and assume that it's close to $100/keg/faucet kit. You can go cheaper with picnic taps but that's not what you're looking for.
Just save your money and get a quality kit, it will matter in the long run that you bought stuff that will last.