that pic is hilarious! I've noticed the same negative camber on other 5ers as well-mine includedI have noticed my 2004 530i appears to have a fare bit of negative camber as well in the rear. I was a bit worried at first but many other 5 series I have looked at look the same. I would assume its factory like that but I guess if you're only getting 8k out of a tire that's not right, does it look like the picture below? I would be interested to know what you find out in an alignment... maybe I need one.
This. ^Negative camber is NORMAL on the rear of your car. It's also NORMAL for the rear tires to wear (on the inside) due to this. You can minimize this be flipping (assuming they are directional) the back tires. Basically, it's a way of life on any newer BMW I've seen. I think you're wasting your money too if you think a (factory spec) alignment will fix this. Setting the rear camber angle to zero will address your issue if you must.