i will tell you this, the s3 is my first audi.
i found out that the car is the most heavy maintenance / repair required brand i have ever had.
i recently talked to an audi / vw specialist shop owner and i was told these cars are amazing.... at needing repairs and maintenance attention.
even if the car sits in your garage for a year without being driven, it will still need attention.
if you saw the shop, it only does audi and vw cars. has a staff of 5-8 full-time mechanics. has a book-out date for any work at an average of 3-5 days. there is enough work that he doesn't need to do any other brands.
we talked about how he has to now fix his daughter's vw car. its newer than mine at 2018. it has broken valve springs. which blew up the engine. he showed me the valve spring. i did ask what is his recommendation on not having that. he said vw doesn't have a solution at the moment. its just a crappy OEM part. i told him an aftermarket one would be better than. he agreed.
you can imagine the repairs he has to do. this is when, last week, i had to install a new mechatronic unit cause mine was defective and finally gave out after the warranty was over. its expensive but i did the whole job myself which saved me a ton of money. i just didn't have access to ODIS (program coding required).
cost for it be repaired, the cheapest i found is about $4k, but can go higher. i would say even at $4k wouldn't touch it. the work that is involved wont justify the amount you make on it. i would say at a minimum, $5k. dealerships are known to charge about $6-$8k.
i bring this up because mech units go out at an average of 150k miles or so. expect it!
ahh but i digress, yes other things have broken besides the waterpump.