We bought a 1998 U-320 just about a year ago. No big failures, worst was a ride height valve failure that happened two miles from the house. I had an extra, replaced it in a couple of hours, and off we went.
Otherwise, we have done A LOT to the coach - fluids and filters, new air bags, vent covers, interior lights and cabinet handles, exhaust manifold gaskets, new insulation in the generator and engine bays, water pump seep, and more. Easily $10,000 of labor if we had hired all of the work out. (I did it all myself!)
It is a great coach, smart and comfortable layout, lots of power, Aqua Hot, looks much younger!
First, you should spend a lot of time reading posts on Foreforums. The wealth of information and expertise alone makes owning a FT worthwhile. Like any older coach, the engine and transmission are the big things.
For a more specific answer to your question... I would not pay $800K for a new coach. I will pay eight cents on the dollar for a used one! No regrets!
Feel free to PM me with specific questions.
1998 Monaco Windsor