I am not an engine expert as some on this board appear to be, that being said people that build racing engines laugh at these high oil consumption post. From what I'm told, high horsepower, slightly detuned race motors burn a lot of oil. Especially during the "break in" process. I'm a member of the BMW CCA and the POC, and I can assure you that the above poster is correct, especially regarding the M5. That 5 litre 394hp motor goes through more oil than Z06's and Vipers combined.
Just my 2cents worth but when you buy a race car for the street isn't it reasonable to spend $45 for motor oil for the first 5000 miles and then $5 for every 2000 miles after that? By the way, if you take your car on the track be prepared to use more oil, brake pads, rotors, etc. than in normal everyday usage.