I don't believe that his argument is alluding to the objects' actual prices, but rather to the framework he perceives MG and Gruber using to further their arguments. Namely, an appeal to 'luxury', where luxury is a self-sufficient reason for something to be better than something else. And that people who haven't experienced this 'luxury' can't comprehend what makes it superior.

Honestly, I haven't read enough from MG and Gruber to form a meaningful opinion on their argumentative style, so I'll digress from staking out a position. But I agree with Topolsky in theory, that is that an argumentative appeal to luxury isn't sufficient in itself, considering luxury can be decomposed and explained at a more concrete level.