When buying a pre owned MB vehicle, it is a good idea to not buy a vehicle with Airmatic suspension, they will all fail as the vehicle gets old, very pricey to fix also.
The standard suspension R has rear airbags for self leveling, still uses regular shocks for dampening. Vehicles with airmatic have a different setup.The rear suspension of all R-class is on Airmatic strut....
Not disagreeing with you and it is really depended on how much you pay and the terms of your extended warranty. I paid less than $3K for my 5yrs/75K miles warranty about one year ago. I have already submitted claims over $3.8K.
#1 reason that I skipped the Caynenne Turbo and bought the R500 instead was because the ability to buy a reasonable priced extended warranty. I am planning to drive the R500 for two more years and without warranty can be very expensive especially my R has a lot of electronic gadgets.