Cheap carpet will be ok for a short while - until someone spills a pot of coffee all over it or beer !! But it is more comfortable than concrete ! How tidy are you ?!?! Maybe have large rugs made of cheap carpet with the edges whipped instead, as at least you can move them, or replace them easily enough ! Most carpet warehouses can either offer to have egdes whipped or know someone who can do it for you !

Concrete would provide more longevity.

PET is relatively cheap carpet that will not stain. It is the pad you have to worry about. Waterproof pad is not a bad idea over concrete anyway. Professionally stained concrete is way way more expensive.