There have been many discussions about repairs and how to decide whether they are economically justified. It would be nice to poll these panelists and others what have been their most expensive repairs and why they went ahead with them.
Mine were a MAACO paint job, including a used fender for $1450 on a 1988 Caprice and a $950 rear main bearing seal replacement on a 1994 Nissan Sentra. In both cases the vehicles were still in excellent condition and the repairs made sense.
1996 voyager in 01, 2k for repairing ac blowup, wifee could not live without ac, 2 years later van gone. Traded in on Windstar, Should have dumped it without ac. Would have made little difference on trade in I think.
but the wife would have been miserable without ac for those 2 years 
and when the wife is miserable, hubby is usually also miserable 
so it was probably worth it, perhaps not financially, but worth it for your mental well-being 
@Barkydog We had to make that kind of decision with our 1976 Ford Granada when the A/C compressor packed it in. The car was starting to rust and my wife drove with the windows open for another year, then we sold the car for $750 rather than sink more money into it.
In 2015 bought a 2003 Wrangler and had a pre-purchase inspection done–but it apparently was done by drunken lemurs. It immediately needed $900 worth of rear end work done. I did it, knowing that I’d probably keep it but even if I didn’t, I couldn’t sell it or trade it with the rear end grinding and roaring and leaking like a sieve. I fixed it, drove it for a year, and traded it for another Wrangler that didn’t need as much work.
'87 Dodge Mini Ram Van. At about 140K miles, had either a blown head gasket, cracked head, or cracked block. Rather than mess with it, I had a shop put in a rebuilt motor. Cost was around $2600 for the 3.0L, IIRC (this was a long time ago).
$1100 to repair my leaky transfer case in my Chevy SUV. Remove, replace rear cover, install new seals, reinstall.
Normally I’d do my own work but it was winter, cold and I didn’t feel up to it.
Thanks for all the frank comments. Deciding when to repair or when to pull the plug is often difficult.
A friend had a Mazda 626 with automatic. At around 90,000 miles the transmission went. The car was in pristine condition with everything perfect. But because of the repair cost ($4200) quoted and the car’s age it ended up being scrapped.
To me the most expensive repair is the one that is not done right. It is either a wrong diagnose and does not address the original issue, or a repair that is not done properly. I have a quite a few examples, mostly on a Dodge Caravan I had. For a non-start issue, the alternator was changed/I should had listened to my gut and refused, but then the starter and so on. After two tows and a few failed attempts, it was a loose started wire.
On the same car, the radiator change had to be done a few times over due to leaky transmission line, crappy part/radiator failure/etc.
A few years ago, someone I know had a 1998 Volvo S60 (I think). She neglected to replace the timing belt on any kind of schedule, despite my suggestions she do so. One day driving to work, the engine completely died, and she was able to coast into a parking lot. The timing belt had broken just like that, and there was severe engine damage. She foolishly sunk $3000 into repairing the car… only to eventually sell it off for a Camry about a year later. The Volvo was a money pit.
98 Jeep Wrangler 5 speed, around 100,000 miles the 4 banger engine threw a rod or something else that made a horrible noise, the 4 cyl’s are known for not lasting past about 100K, had a junk yard engine and new clutch put in. About $2,800. My son still has it and uses it for fun, he has much newer daily drivers.
Anything that requires large things to come out of the car or a lot of surgery to get to. A water pump is a very cheap part, but on vehicles with timing belt-driven pumps, there’s so much disassembly involved that you could often, literally, spend less on a week long Caribbean cruise.
It’s especially fun when something breaks behind the dashboard, particularly in modern cars where getting the dashboard out involves hours of work to be done before the mechanic even starts working on the thing that’s actually broken.
But the most expensive repair is probably when the mechanic replaces parts almost at random because a computer told them to or because he assumes he knows what the problem is without actually bothering to test his hypothesis, and ends up taking 5 or more tries to get the car working right. That scenario is actually what got me started working on my own cars, because a mechanic (and I was even doing the right thing and going to a local, independent shop!) spent well over $2,000 of my money throwing parts at a stalling engine when all he had to do was replace a $100 fuel injector.
I guess I’ve done a diesel engine or two for $2200 and $1000 and have done quite a few transmissions for $800 - $2200. If you are running 30-40K a year and the car is good otherwise and don’t want to just spin the odometer on a new car, these are simply normal repairs.
@bing Thanks. Each situation is individual. I recall working with an instrumentation sales tech in Texas who put on an extraordinary number of miles servicing the oil industry,
He had an 80s Mercedes E class 300 Turbo diesel. He had to spend $5500 on a new transmission at one time, but with the very high fuel mileage and the rest of the car being in great shape, he spent the money and happily went to over 400,000 miles while getting paid mileage by his company. The car had to be spotless and reliable; two company requirements. A tech expert driving a Mercedes bodes better than having him drive a Lincoln Town cCr.