I have been trying to buy a Hot tub for over a year and the more I know the less sure I have become.
"It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so." - Mark Twain.
I've been meaning to make that my new sig.
You can buy a lot of great tubs in that price range. I would say that the VAST MAJORITY of Hot Spring customers are happy with their tubs.
Most of the Cal Spa buyers are happy with their tubs.
Some of the Costco buyers are happy with their tubs.
And as others have said, I would imagine that the Hot Spring prices you're seeing are "MSRP". By the time you haggle with the dealers they should be a fair amount less. You can get all kinds of high-end, reliable tubs in many places around the country for $9000 or so. Many near-top-of-the-line to middle-of-the-line tubs are $6000-$8000.
I would say that most people on this board would say that Hot Spring is one of the best tubs out there. MOST would probably not put Cal Spa or Costco tubs in that category. Sundance, Jacuzzi, Caldera, Marquis, Arctic, D1, and others are usually considered to be among the best.