From what I was told it had to do with it being a wierd size and special sensors.
IMHO European cars are not driven as many miles per year (in Europe) and have a longer lifespan in Europe because of less usage, but when brought to the USA see much harsher treatment in the form of road quality, miles driven, and driving habits by Americans and so require more maintenance and have a higher failure rate.
The Cooper at 80k miles is probably got a lot of life left in it, at least a few more years before something major happens, it would make a great 2nd car for fun, but might be a mistake as your only source of transportation, of course this is just my opinion.
You forgot temperature
extra weigh of the occupants..
The only thing i can say is that the 1.6 THP engine used in the Mini cooper from PSA Peugeot not BMW,
realy has a bad reputation unfortunatly.
And the gearbox are also a point of attention with the models prior to 2004
Here is a Dutch buyers review about the Mini with English subs.