I cant argue that the purchased racks aren't nice, or that the pros don't all use ARS or Freedom Breeder type steel frame suspended racks. However, if money is tight nice racks can be built for less. I built a rack recently using 1/4" XPVC and wood combined. I got the design and DIY build instructions from this site.
http://northeastsnakes.com/racks.html
The one I made ended up having 7 Rubbermaid 15 quart tubs in the top section and 7 Sterilite 28 quart tubs in the loser section. Can be heated with back heat or belly heat. I used boards that came pre primed in white for a nice all white finished look. You could paint the wood black and use black XPVC just as easily. All in with heat and casters was less than $200.