From my knowledge of European engines... When it reaches 30,000 Miles or 50,000 Kms.... It becomes expensive and unreliable. They are highly strung From the get go hence why you see 2.5 lt turbo engines with 400 horse power and 400Nm of torque from low revs... The OEMs crank it for performance rather than reliability and durability.
That is simply not true. Current MQB VW/Audi leave a lot on the table. Start with a GTi that is about 220 whp stock. Those hit 300 whp with a downpipe and tune. No reliability issues.
The 2.5T in the RS3/TTRS are hitting 10s easily with bolt ons. 500 whp.
You can blast the germans for high maintenance costs and I will not fault you. But, they leave a lot on the table when it comes to boosted motors and tuning