I love stories like this, one of my best friends is a mechanic and has been for 20 plus years now and Ive spent 100s of hours exchanging stories like these with him over the past 20 plus years.
And your story just confirms what me and sertac just said, mechanics here just love Jap crap cars because quick in and out no real diagnostic equipment or knowledge required translates to quick money.
Let me tell you a story also. Soon after I bought my L322 Range Rover, developed exactly the same problem, key would not turn to start,and was also told I need an entire new steering column new security ecus, ignition and door locks along with new key, and as usual I told them to EDITED.
Upon investigation the steering lock actuator had broken and wasn't giving the ecu the car is safe to drive signal and thus the key lock wasn't retracting.
I then ripped out the entire key cylinder dismantled it and took out the lock at put it back in now the key would turn car but still wouldn't start, so found out it could be the block with metal contacts below the barrel that can also go wrong.
Scrappies wanted 1200 for it and I said EDITED. Further investigation ensued and found out its the same part used in all bmws from mid 90s to early 2000s so went to an afghani in shaj who has tons of right hand halfcuts got the part for 50 dhs but the connector shape was a mirror of mines but pins were same, so 10 mins of filing the plastic down and put ir back and now car runs perfectly.
Now if I would have gone to majority of grease monkeys over here that call them selves mechanics my car would probably be standing exactly like your buddys Audi and I would have spent a few thousands also.
And this is one of the many many times Ive been told by mechanics that my unrealiable luxury european import will require a truck load of money to fix only for me to have fixed it for virtually nothing or very little.
So dont blame the car, if the mechanic doesnt know how to fix it!