Repair cost on common problems

My C180 Mercedes went in for a v-belt, tightner pu and belt tension, the three parts they replaced, labour cost R2922.50 for 3.5 hours work.(R835.00 per hour) Parts R3000.00. Then I had to find out my timing chain need to be replaced cost R35000.00 (Thirty five thousend), the only inspection not been done with Mercedes while the car is under a motorplan or with regular services, mine is 7000 km out of it. This is actually a common problem on the C180 and the C200 cause it only got one chain and the life span round about 100-120 thou-send km's. Further to find out the electronic in the steering and engine compartment also a common problem, parts cost also +/- R6000.00 without labour. Look I am in for a surprise and how many other owners with this 'common' faults that Mercedes is aware of and does not want to take ownership. DEFINITE my last Mercedes with the superb technology.(sic).