It isn't only BMW dealers. I've had a few of these experiences. At Monte Carlo auto, I was clearly interested in the E61 they had (BMW M5-GP) and made an offer. They said it was impossible. 3 weeks later, car was marked at the price I offered (no call - I spotted it myself)... I called again and then there was some story about not being quite sure whether the car was for sale or not... owner being overseas etc... 2 weeks later, I gave up trying to give them my money. Won't go back.
Melrose Nissan actively talked me out of a GT-R... TWICE. The spot next door (which has reinvented itself a few times) was never interested in getting back to me on trade values or test drives for various cars over the years... not even cheap ones... their losses.
Jaguar Midrand (and subsequently SA when we escalated) threw away R2M worth of business because "nobody buys base F-types" (2 of us went and were keen). In the same breath said nobody buys XJs because they are too expensive LOL. Went with pre-approval. Could not test drive, no discount on the cars that they wanted us to buy (several HUNDRED thousand more than the base car with the key options which we were keen on). Salesman said we should drive the coupe as it was identical to the roadster...
On trade ins, Honda dealers were offering to buy my S2000 for R165K. Nobody (even when they had agreed telephonically) would work on a consignment/comm model. I ended up selling the car on the day I advertised it for more than R70K more. I would have taken the deal at R200K for simplicity's sake... but they would not budge. Same dealers have cars with more mileage marked at R250K. Greed.
Many more dealers have poor business practices... could go on forever. Many salespeople are crap but there are a few great ones out there too!