I agree with you on the food chain being different yet its not totally dissimilar. On the Eames chairs the markup for the retailer is about 40%. Thats quite a lot considering its a chair.
Kitchens are ridiculous and you are correct 70% is well within reach. I got a 10k kitchen for 3.5 a couple of years ago by playing two rival retailers off each other where one accused the other
of breach of "price fixing" agreement with the manufacturer.