I am contemplating purchasing a late 80's to early 90's BMW 525 or 635
series.  I have been told that it is very expensive to maintain a BMW.
 I know that I will encounter maintenance issues with a car of any
make that is this old.  However, will a BMW of this age cost me
substantially more than a Toyota Camry or a Honda Accord of the same
age to maintain?

Here is a comparison of common repair costs for the three vehicles
that you mentioned.

***1990-96 BMW 5-Series***

http://auto.consumerguide.com/Auto/Used/reviews/full/index.cfm/id/2118/act/usedcarreviewreliability/

Item Name Repair Cost 
A/C Compressor $1,280 
Alternator $610 
Automatic Transmission or Transaxle $1,150 
Brakes $255 
Clutch, Pressure Plate, Bearing $875 
Exhaust System $1,015 
Radiator $710 
Shocks and/or Struts $865 
Timing Chain or Belt $1,920 



***1990-93 Honda Accord***

http://auto.consumerguide.com/Auto/Used/reviews/full/index.cfm/id/2047/act/usedcarreviewreliability/

Item Name Repair Cost 
A/C Compressor $530 
Alternator $355 
Automatic Transmission or Transaxle $1,055 
Brakes $250 
Clutch, Pressure Plate, Bearing $550 
Constant Velocity Joints $670 
Exhaust System $465 
Radiator $485 
Shocks and/or Struts $545 
Timing Chain or Belt $350 
 

1992-96 Toyota Camry

http://auto.consumerguide.com/Auto/Used/reviews/full/index.cfm/id/2105/act/usedcarreviewreliability/

Item Name Repair Cost 
 
A/C Compressor $865 
Alternator $375 
Automatic Transmission or Transaxle $1,067 
Brakes $145 
Clutch, Pressure Plate, Bearing $600 
Constant Velocity Joints $500 
Exhaust System $550 
Radiator $580 
Shocks and/or Struts $800 
Timing Chain or Belt $220 


Many of the repairs or substantially more costly for the BMW, most
notably the "Timing Chain or Belt", which is more than 8 times as much
as the Toyota.  I did look at a few other BMW models in that era on
that same website and they had similar costs.

Given this information I would conclude that the chances of spending
"substantially more" on the BMW in the long run is statistically true.

Please let me know if you found this information useful.

Thanks!

Thank you very much.  This is exactly what I wanted

My stepsister has owned several BMWs. She once mentioned that she they
were quite reliable, and were low-maintenance as far as the number of
incidents that required service, but when service was required, the
cost was often high because of the price of replacement parts.

Wow! I need to increase my prices!!!  I guess those must be dealership
prices in New York City or something.  In Florida we get about half of
those quoted prices.

Nevertheless, the proportions are about right, with one exception:

Although I would recommend a Camry ove a BMW, the "8 times the cost
for a timing belt/chain" figure is misleading!

There is a BIG DIFFERENCE between a timing chain and a timing belt!!!!

A timing belt should be replaced every 50,000 to 80,000 miles
(manufacturers differ in the recommended interval: see my article
http://econofix.com/tbelt.html) whereas a timing chain such as the one
BMW uses is normally good for the life of the engine. (At least
150,000-200,000 miles)

Thus that particular spec is an "apples to oranges" example.

The advice is still good, though: I'd recommend the Camry over the BMW.
The Bimmer, though is a quite solid and well engineered vehicle, and
it for sure has a higher "wow" value than a Camry.  Because there are
more Camrys on the road than BMW's  you would be able to get parts
from an aftermarket supplier rather than being forced to get things
from the dealer.

Why do I prefer Toyotas to Hondas?  One of the many reasons is in that
timing belt: almost all Hondas will bend valves if the timing belt
breaks, whereas practically NO Toyotas do. Although if you change the
belt when you are supposed to this isn''t a problem, this to me
indicates a design "attitude".

Toyota wants to build a car that will "take a beating".  Honda, like
many other cars on the market, doesn't have that goal so much in mind.

I can tell you of many Honda and Nissan "nightmares": $500
distributors that trash out at 75,000 miles and can be obtained only
from the dealer come to mind immediately.

So I would recommend Toyota without hesitation, BMW also, but be
prepared to pay a bit more, and I'd discourage the Hondas and Nissans.

I'm an ASE certified master mechanic, I have owned my own shop for 30+ years.