The Flair price is more than fair. I'd say it's to low. It also shares the same warranty as the Hot Spring Highlife series, which is great. Plus you know Watkins will back you up.
The Sundance is a good spa as well. Great company. Can't say to much about the price, but it seems like it is within the range of what it is normally sold for.
The LaZ boy is something is not something I have looked very hard at. I imagine it's like Coleman spas, where someone makes it behind the already established name. I wouldn't expect them to be nearly as good in the service/support department as Watkins or Sundance. (I'm talking about manufacturer, not dealer.)