I will third the used market.
I actually got mine for free, but had to put about $600 into it for parts up front -- paint, new control pack/topside, 1 new pump, and a new cover, all from ebay and DIY assembly. We have probably put another $150 in parts (plus DIY labor), and then just got a new cover ($250), so total into it is $1K for a free tub and 4.5 years of use.
It's sure not the highest end one out there, and is probably 15-20 years old, but it works for us!
Electricity hit hasn't been too bad, but we live in a warmer climate and run it as a cool spa in the summer.