I mean, it does feel bad for the luxes to be poorer, but can you really blame the AI for not trading for luxes it doesn't need at all? Especially when perfect play at high difficulty is to sell early luxes (even singletons sometimes) very aggressively to take advantage of this? I think a better solution would be to balance happiness differently at different difficulty so the AI was sometimes unhappy and sometimes actually needed luxes, than to artificially force the AI to pay a high value for them to inflate the economy.