Where I was working in 2000, unsure what the basic was, but it was �50 per car (all used then), plus your extras if it was financed, warranty, etc.
Given that we'd come into the service department almost every Monday to find at least 10 cars sold over the weekend alone (between 3 salesmen), and they'd generally sell at least another 6 between them during the evenings, they'd make a tidy earning on commision alone.
Would also agree with LCD - the margins on some cars are very narrow - we used to sell a lot of BMW's and Daewoos - completely different ends of the scale, but good margins on both of them as well.
I would have thought basic is at least �10k now, if not more, which isn't too bad in itself dependent on your location in the UK