What mileage did the water pump fail at? you have to replace them every 60k miles sounds like someone fail to keep up on the matinace...
I have had 3 Bmw's
1986 325es (Total Cost including cost of car except gas) $286(not a typo) for 30,000 miles
Issues
Timingbelt waterpump(maintince)
Main relay
1999 740iL (est. Total Cost including car except gas) $13,570 got at 126k mile currently 153k and some change
Issues
Water pump exploded(Wasnt changed at 120k like I told it was

)
Drag link and thrust arms (shimmy)
Timing chain Cover,Valley Pan, Valve cover gaskets, Headlight bulb, and solved all oil leaks and flushed the power steering system.
1987 635CSi (est. Total Cost Including car except gas) $1,500 got at 244k is now at 245k
Issues
Shocks and springs strut tops in all 4 corners, and slotted the rear subframe for adjustablity
Retrofitted the A/C system to R134a
Redyde the interior panels
New front speakers,Deck, wiring, 4 channel amp, 6x9 rear speaker retrofit and wired for a sub behine the rear cooler
Main relay sketched