Maybe the amount of our pleasure with Giza pyramids already exceeded the pain invested to build them. I don't know. Can all the pains of a slave be justified by all the pleasures of the tourist, visiting the hole in the rock, he was forced carving for 50 years?

Was it that much pain? I read in National Geographic, IIRC, that the modern archaeological conception was that the pyramids were mostly or entirely built by paid labor - Nile farmers killing time during the dry season. This may even be a good thing, depending on whether it diverted imperial tax revenue from foreign adventurism into monument/tomb-building.