it does not matter how much it cost as long as player can spam free generators and sit AFK.
only valid solution for such items - additional consumable items produced in reactor, as fusion byproduct or direct output or something similar, but process shoud require direct player interaction (not possible by staying AFK)
actually this is good plan, some items with cost more then 1kk EU require neptunium lens to assemble, lens consumed in process, profit!
ever if player have hurge solar plant, he just can't craft nether star due lack of neptunium lens required for process.