New reactors usually require a lot of materials used each cycle. So, to properly calculate it's effectivity we should know energy price of making replacements. Especially if we use lapis. And for that, we should know the price of making scrap.
If we'd have rp2 (i.e. breakers), then it would be only price of recycling - 12k per matter or so, because we can feed recyclers with generated cobble slabs.
But how to make scrap without block breakers?