I had a 6 person Coleman hot tub. Coleman was up there with the Caldera, Hotspring, etc. (Ours cost $5,500.) It cost - at max, about $20 a month to heat - and that was in the middle of winter (Northern IL - it sat outside). The only chemicals I used were chlorine and muriatic acid. I had originally bought all the fancy crap that the hottub dealer recommended - but found online that alot of people used chlorine and muriatic acid as their only chemicals. (Muriatic acid can be purchased at any hardware store like Lowes, etc., and chlorine at a pool or farm supply store.) Chlorine was about a shot-glass full, and muriatic acid about a cup. That was perhaps a few times a week. We had it for 3 years and used just those chemicals with much success. You'll also need test strips - about $10 for a few months worth. It's a good idea to have a spare filter and some filter cleaner - you can soak one filter in the cleaner while the other is being used. Filters can be pretty expensive.. I think mine were about $50.
I loved our hot tub - sold it with the house tho. My boyfriend has a portable "Softtub". Not quite as nice, but does well. It was about $3,500. It runs on 110, whereas mine ran on 220.