I don't know whether that is a fair price. CruiseAmerica tends to be pretty market aware and prices to sell, but that mileage is an unusual market segment.
Too much mileage? Depends on how you will use it. If the idea is to drive out to the campground, 50 miles every weekend (the way I'm using mine, only it is 15 miles andabout 8 times a year) then a 150,000 mile chassis is not too worn out, maybe 10-20 years worthof short trips left in it.
If your plan is to start touring the country full time, or even a 3000 to 5000 mile trip once a year, I would recommend looking for lower mileage. In the first instance because younare looking at only one or two years worth of costant use, the second because you likely want more reliability for an annual long trip than you get with high mileage, unless very carefully maintained, which doesn't happen with once a year use. Yes, there are Ford E-series vans and box trucks in regular use with 200,000 to 300,000 miles, but that is regular use and regular maintenance, repairing all the little problems as they come up. RVs tend not to be used that way.
There is another side to this. Most of my maintenance costs have to do with things that deteriorate in storage: rubber like tires, belts, hoses, seals in engine, transmission and other running gear, and metal corroding, as in brake calipers and pistons. A 150,000 mile unit in constant rental service, this stuff gets taken care of as it happens.
