So the average energy gate costs 3 energy and has 2 red boxes behind it, right?
Seems like a bad deal, but technically:
Let's say for argument's sake you get a set of shinings every 3 gates you open (9 energy).
Shinings come in sets of 3, and are sold 50 for 350 energy.
Quick maths:
350 * (3/50) = 21
So each set of shinings is worth 21 energy.
This technically means that in tier 3, you'd have to get no rarities for 7 gates straight for it to be "not worth it".
And in the case I said earlier you're essentially saving 12 energy.
So yeah, you should actually open gates (even if it means putting your energy at a non-round number)
(everyone already knew this already didn't they)
Well, the crowns that drop from monsters alone are enough profit, I think they drop about 400-1200cr per room in T3 I think. I usually just do them for the fun of it TBH. The radiant pay in them is pretty decent as well. But yeah, I agree that opening an energy gate is never "not worth it" unless it just leads to a few boxes below D26 or is at T2. But I don't agree with your Shinning Fire Crystal argument as they are almost totally useless end-game.
Edit: Oops, I thought you were talking about danger rooms... But really, why would Shinning Fire Crystals matter to a vanguard if they can't benefit from them because they already have tons and they can't sell them?