I agree, but, I believe it's unfair to compare the two. By the time you've added a few bits and pieces to the basic £48.5 for a Cayman S you're really looking at a car that's going to set you back £55k or probably more....and last time I asked a few years ago the discount for cash was pitiful. A 370Z will set you back £33k with the GT pack, you can probably get a big discount on that too. A better comparison would be 370Z against the Boxster, Cayman S versus GTR.
Pete