If your talking about the sumps the LFS wants to sell you with the chambers for the bio balls etc. Yes they are a rip off and of questionable effectiveness for reef tanks.
However you should be able to find a 600GPH overflow box for around 40 bucks, a 20 gallon tank for 30 and a return pump rated for 600gph for another 30 and hard plumb the return for about 5 bucks.
For my setup I place a piece of eggcrateing across the top of the sump. Put filter media on top of it and direct the water coming from the overflow so that it runs through this media before entering the sump. Easily changed filter media means the likely hood of doing just that goes way up. From the pic it looks like its time for me to do just that.
Sumps have a lot of benefits. Expanded water volume a place for your skimmer, heater etc. The list goes on