Live rock is expensive, base rock is pretty cheap though. You could get 20 lbs base rock for $40 and seed with a couple pieces of small live rock. It would be very tough setting up a tank on that budget but it could be doable. So: rock-$40, sand-$20, powerhead-$20, salt-$20, hydrometer-$10 you would probably go over that budget though by a little. You'd need the heater, filter and light still.
20 Gallon SPS reef
29 Gallon FW "fat catfish" tank
20 Gallon Long Dart Frogs "Zig" and "Zag"