I would second the Grand Wailea - it may not be cheap compared to home, but it's as reasonable as you're gonna find for such a nice spa. I went there 2 years ago and just did the Terme Hydrotherapy baths. I spent a couple hours in there, soaking and trying all the different baths, rooms and showers, etc. As the previous poster said, the Terme is also included as part of the other treatments (massages, wraps, etc.) In between they provided bottled water, fruit and chairs to lounge around in and relax (in your robe). Excellent value - and it's a large enough spa that a group of friends could hang out in between treatments.