In fact, the only way charging different prices to different customers - or offering different wages to different workers - makes sense is if you're living in a socialist utopia.
After all, a core tenet of Marxism is "from each according to his ability, to each according to his needs." In a just society, people who need more get more, and people who have less, pay less:
https://en.wikipedia.org/wiki/From_each_according_to_his_ability,_to_each_according_to_his_needs
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