I kindly agree with you but what is annoying for me is that it had drained in like 12 hours and dead when the engine was still on. I thought that while the engine is running the battery is charging.You need to meter circuits to trace the drain.
If I want to look at the alternator it means that I have to dismount the hole muzzle of the car. Last time it costs around 1000$Sounds like you've been chasing an on-going fault without proper diagnosis. I'd be looking at the alternator.