I think that's actually kind of a misconception about Porsches. At least 911's up to the 993 (1998). Their interiors were spartan as fuck. Not cheap, per se, but just completely bare bones.
Granted, that's a 15-20 year old car at this point, but I don't see it being any fancier than a similarly aged Corvette:
Although that Corvette interior is pretty horrifically fantastic plastic. In any case, after the 993's Porsche pretty much went from being a low production sport car company to a high production luxury car company, and their interiors changed accordingly.