I do not know of any way to do cheap reefing, especially with corals. Perhaps you should define cheap. I consider a 120 gallon set up compete and ready for fish with out controllers or electronic monitors cheap at $7500. Controllers and monitoring/testing equipment add nother $2500. Of course there are also the fans/chillers, RODI filters, quarantine tanks, water holding tanks, reference books, live food culturing systems and then the corals. $12000 to $15000 sounds pretty close to me. I have never been able to figure out how to do cheap reefing, really.