After processing tons of Fuel Cells for Engineering, I realized that the amount of Fuel you get from the higher tier recipes is not worth the amount of power crystals you put into them. I figured it’d be better to equalize the amount of fuel per crystal to make the higher tier recipes worth using.
At the moment, the recipe for x15 Fuel Cells is the most efficient at a cost of two power crystals per craft. The recipe one tier above, x20, costs three crystals. It’s immediately a waste and it only goes further into waste as the recipe for x25 costs four crystals and x35 costs a whopping five crystals.
Personally, I’d scale it by intervals of 10. You might get more fuel cells being created in general, but given how some things consume insane amounts of fuel, it should be a net positive overall.
x10 - one crystal
x20 - two crystals
x30 - three crystals
x40 - four crystals
x50 - five crystals