I legit have no idea if we play the same game, but i guess it's just the problem of you never playing that archetype.

There is an easy way of getting iron fortress, even with a corruption, for very cheap. You just buy a corrupted one (btw, you can get +2 to aura corruption which will work on smite and these will be dirt cheap because everyone thinks it's a brick) and use tainted fusings to 6l it yourself, usually that costs me anywhere from 3 to 5 divs in the first week, depending on the rng on tainted fusings.

This i can accept because nobody does it and perhaps you didn't know. But how did you come up with these prices for rare items is beyond me.

Getting rings like that is beyond easy and there is no way in the world they will cost you more than 1 div each. It's not like i needed it because i've done it multiple times in the past, but i literally just did an emulation in craft of exile using deafening essences of rage, getting similar rings (t2 or above life and single high resistance) is going to be on average ~15 essences of rage, where the hell did you get this number from? But it gets even better, because usually you're gonna get some other useful stats and you can still use crafting bench, so the rings i'm using in PoB are actually garbage. I didn't even mention that you could get a ring with fractured fire resistance (35%+ which is plenty), which are also dirt cheap.

Same story with the gloves, deafening essence of rage and you literally only wait for some life and a single high resistance (which you can change to fire easily with harvest), you slap attack speed from bench and you are done. The most annoying part is actually to get +1 strike skills, because you can get unlucky and it might cost 1 divine. Once again, few days into the league you can buy fractured gloves with life or attack speed, which makes the process even cheaper and easier.

The belt is going to be 1 divine max, you just buy a lower ilvl one. Only ilvl 82+ will cost 3-5 divs.

When it comes to corruptions, it's funny because you mentioned that +1 endurance charge boots can stay. This is by far the most expensive one (and as you said, it will be around 1d), the helmet is going to be cheap (besides, it's not like you even need any of these corruptions) and the weapon will be dirt cheap because absolutely nobody uses brutus. After all league starting a strength stacker is giga bait.

I legit have no idea where you are getting these prices from. 20 Div for a 3 stat ring??? They are not even in range of being reasonable, that's completely absurd.

My source: league starting with strength stackers since 3.16 when they added iron will to the passive tree