Hopefully I can shed some light on this subject. I had the same issue with my 11' 135i about 3 months ago and had at least 4 trips to the dealership in 2 weeks.
Option 1: Never go with what a dealer charges. (Break My Wallet) is only true if taken to a dealer for PARTS, labor is different.
Option 2: I did this for a week and the stupid warning light kept popping up with that dinging noise and it drove me crazy. Also the adjust feature can sometimes leave your headlights in a weird position, still pointing straight but it looks off.
Option 3: Did not think about this, could be a good idea but will always know in the back of your head that they don't work.
Option 4: As tricky as BMWs are with electrical systems I wouldn't go this route because you have no idea what other codes could be thrown for xenon or whatever.
I ended up buying replacement VALEO headlights. VALEO is the original manufacturer of BMW e8x headlights. Only difference is no BMW logo stamped onto them. Also instead of $1000 for one headlight you can find them from $499-$599 per headlight.
Search these part numbers with "BMW" before or after and you'll be able to find what you're looking for.
left: 63127164931
right: 63127164932
I also needed to purchase a 63117180050 control unit for both sides, the headlights come with the electronics box but it does need to be coded. I believe the headlights come with the xenon bulb as well.
I had my dealer insist that I don't buy from a dealer, lol. They were able to install them and code them for me for free. (They messed up my car previously which is why it was free.) If you can find a reputable BMW shop that has the right tools to code them Id go there if the price and labor is right.
While your add it, like me, you should replace your DRLs(Halos). The stock headlights have that dumb amber color.
www.luxangeleyes.com offers a great set! I got the color adjustable ones and leave them at around 7,800K and they are so bright If i unlock my car at night people have to cover their eyes lol.
Hope this helps man, I had a huge headache dealing with it myself and didn't find any threads on it either. If you have any more questions let me know!