Trunks, you also have to remember all the varient covers and incentive covers in that 'total cost' you quoted. All of which is included inside that $35 single compilation.

For me, all the incentive covers and multiple cover varients, that were intended to *increase* sales, actually prompted me to stop buying the regular issues and get the compilations instead, to get all those different covers. I wanted all the different covers for the artwork, but have always hated having duplicate *whole* comics just for a new cover.
So the concept to increase sales, actually encourages people like me to not buy them in favour of the cheaper TPB option that includes all the 'expensive' extra cover versions in it for less.