I got the ULTRA cheap kit from walmart about 4 years ago for like $27. The stand wasn't any where near as nice as the bayou style. My base was just barely big enough to set a converted keg on. I have no idea what the BTU rating is, but it can bring 5 gallons of 65*F water to a boil in 25 minutes with the lid on and maintain a nice boil on a batch with no problems.
The pot that came with mine was a piece of crap, too. I sit my mill on top of it when I grind the grain and sometimes put water in it.
Something eventually went bad with the iron burner, probably because I didn't take good care of it and left it sit outside all the time tucked under the grill cover. It started to burn really bright orange flame and left greasy black soot on everything.
I replaced it with an equally cheap used fryer off craiglist which I still use when I brew a friends' houses.
Ground Fault Brewing Co.