I bought my Overland when it was 13 yrs old. It is now 17 yrs old.
I do a lot of the work my self with the exception of major things like dash a/c rebuild, Allison transmission computer problems, manifold gasket replacement and rear end differential replacement. I have $10-12 k in these items. I have fixed countless other items - I pretty much am working on it constantly. Some of the items like slide repair and Big Foot leveler repair would have been quite costly in labor. If it goes to the shop I expect it to be a min. of $1500.
My rig cost $36k, so the 50% estimate above is probably quite accurate.
But I could 't buy a rig of that quality for $55k, so I have no regrets and I enjoy doing the work.
If you don't do your own work it will cost double that not counting all the time taking it to the shop and waiting for a week before they work on it.
And remember you don't know something is broke most times until you are taking it on a trip. Shops can ruin a lot of vacations with the time to have them fix it.
My 2 cents worth.