Buy used? Seriously, you will not find a quality rack for cheap, even if you buy used, but if you shop used your odds do go up some. I picked up a TopFive rack for $150 last year, in good shape. Every once in a while a Garvin or KargoMaster will come up for sale used, and both of these are good.
None of these racks will make it fun or easy (or in some cases even possible) to fold your soft top back. Keep that in mind. There is no free lunch here.