I’d say we’re nerfing not just energy income, but remote energy income. When we designed all the energy costs and sinks in the game, we weren’t considering the fact it can become so easy to reserve and mine 10 remote rooms per one claimed room. It was our design flaw that is revised now.
Among other things, I thought that was a good thing, because it means those rooms are not claimed, and that limits the # of minerals being mined, which certainly seems to be something your proposed changes indicate you desire.
In Screeps, selling and buying is not a result of surplus (there should be no overall surplus of minerals at all, it means that game generates more minerals than it can consume), it’s a result of balancing between different mineral types in order to get proper compounds as quickly as possible.
Fortunes are made or lost over localized imbalances in distribution.