The problem is that an upper-bunk kupe now costs effectively the same as a platskartny. That should have the effect of making it harder to get these tickets on short notice. And as my Russian officemate commented, what are you going to do when you pay the full tariff for the lower bunk, and the babushka with the upper bunk asks if you don't mind switching? (I never minded switching before, but somehow knowing I've paid twice as much will make it less appealing....)