Try at least 220 lbs (1 lb per gallon) if you want to do a reef, and 2 or more lbs per gallon would be best. So adequate rock for a reef would be 400 lbs. This is an estimate, since better rock is more porous, takes up more volume and weighs less.
9 dollars/lb for ANY rock sounds outrageous. My rock was 6/lb and it was of very high quality.
I think you have a misconseption about fowlr also. For a true fowlr tank you will need at least 1 lb of rock per gallon also. Your live rock is your filtration, you can NOT skimp on live rock in any set up that's relying on the rock and sand for filtration. You will only have problems, and believe me you don't want nitrate problems or any other problems in a 220g tank. You don't wanna be doing huge water changes on a large SW tank to fix problems stemming from inadequate rock.
I wouldn't recommend a wet/dry, but you will have to go that route if you aren't willing to buy that large an amount of rock. With a small amount of rock and a wet/dry you're going to have nitrate problems which will limit the types of fish you keep. You'll have to go with hardy nitrate resistant fish, and if that's fine with you, good, but just keep that in mind.
As far as where to buy cheap live rock. Try reefcentral.com, see if there's any saltwater clubs near you, or any people that live near you that can help you out with this. You'll want to make sure the rock is quality too since stores will often sell "live rock" that is little more than poor base rock and is extremely dense. Not a good option.