I've been looking at Liqui Moly. I don't know the price but their website and promotional material say "for BMW M application." It's the No.1 oil in Germany and I am sure it's TUV approved and also meets most OEM specifications. If it's cheap and given I hardly track the car, and change oil every 12 months/6k km, I will be going with LM from my next change.
2007 E92 6MT - Silverstone II with /// Performance Exhaust with ACM Test Pipes and BPM Sport Stage II Dev-Tune - Proper engine warm up, 12-monthly oil change, Castrol TWS 10w-60
2014 F15 X5 3.0d