It is always much cheaper to buy 2 of the same level than to increase the level. Increasing a level is 2.5 of the previous cost and it *accumulates*, so the total price of a level 2 is 3.5* one (although this diminishes), where it is 2* one for two of the same.
Fun fact if you put the feedstock production right next to the factory that uses it no roads are needed. There are some weirdnesses though when buildings are close, especially with power plants -- sometimes factories pull from certain power plants and ignore others even if it means sub-optimal power. Also some combinations, like a coal quarry next to a power plant, need to be "primed" with a road/warehouse/tunnel but once going they can be removed.
This is the minimum to generate a self-contained 1 fiberglass/sec:
17 Woodcutter -> 14 Charcoal + 14 Iron Ore -> 12 Iron; 13 Sand -> 9 Glass; 10 Coal + 12 Oil -> 7 Plastic + 10 Water -> 1 Pultrusion.
Energy production needed: 1,112,976 -- I did this with five solar panels: a 7, a 6, a 4, a 2, and a 1; and two hydros: a 9 and a 16.
I also set up a self-contained concrete production of 1 with 11 Stone, 6 Sand, 5 Water, powered by a 4 Hydro and a 9 windmill.
I did these with no pipes or cables except for connecting to the oil rig out of necessity. I did use roads, but by and large I connected resources via adjacency.
There's weirdness going on when you put multiple power plants next to multiple buildings, where sometimes the building will draw from the stronger plant and totally ignore the weaker one, even if by doing so results in less than 100% power. So some spacing was needed to avoid these quirks.
The energy emitter doesn't buy you anything, since cables can already go over mountains. I guess the only benefit is that when you get cable-screwed due to the escalating cost in steel, you can instead use fiberglass, which is a pain in the neck to make. But that will only save you a few batteries here and there.
buggy... construction upgrade requirements complicated... can't upgrade metal storage without more metal... huh??
I played this game before, it was called Backyard Monsters... and it got old real fast when i realized it was futile.