If Sky were to offer a motor sports channel which included F1 in the basic deal how many would sign up. From their web page the Basic package is GBP 19.50 or GBP 29.75 for the HD option. The basic option would then price the cost at GBP 23.40 per race for the 10 races not covered by the BBC. (HD 35.70)
My thinking is they would get many more people to sign up and therefore BSkyB would make more money, than having F1 on one of their normal sports channels, which cost a fortune, (GBP 20.25). The cost for each of the sky covered races if you had to pay for the sports channels and wanted HD is GBP 60/race.