Is using weapons on troops worth it

I think I can be considered a rookie as in I've read a lot but I haven't really been through a war so I'd say that I'm lacking experience. Lately I've been doing some math and research on mass weapons production so they can be equipped to troops rather than commanders.

I've been using the tables on Ten Kulch's profile regarding equipment and analyzed the first few recommended equipment items (green rating). I've aproximated the cost of each equipment based on the market cost of each element at some time, and skipping the most cheapest offers to simulate for the long term cases when those won't be available.

1. Plainsman's Spear: Spear (~75 gold) + 10 gold + Scaled Charger Vertebra (~13000 gold) + Herb (~400 gold). In total I have a cost of 13485 for an item that would raise my spear unit by 60% on Plains. For reference, the estimated cost of a human T2 Spear would be 1325 gold. So I'm spending 13.5k to increase the stats of a 1.3k unit by 60%, and only on plains.

2. Plainsman's Armour: Leather Armour (~300 gold) + 10 gold + Hide (~4500 gold) + Giant Scorpion Exoskeleton (~15000 gold) = ~19810 gold. I can use it on an archer for example to increase it by 60% on plains (or 100% being human) but that archer would cost me ~607 gold otherwise.

3. Forester Spear: Spear (~75 gold) + 10 gold + Giant Rat Fur (~3000 gold) + Herb (~400 gold) = ~3485 gold

4. Short Sword: Sword (~285 gold) + 10 gold + Giant Rat Fur (~3000 gold) + Mineral (~200 gold) = ~3495 gold

So you see where I'm getting at. With some of those items I pay about 10 times the cost of a single unit and I only get a 60% bonus on plains. And I know that you may be telling me that the costs I took from the market are way overpriced and I could get a better deal but still I doubt I could get a deal that's 5 times better or 10 times. And if I get a better deal on a Giant Scorpion Exoskeleton, I might as well get a better deal on simple spears or leather armours and this lower my estimated troop price as well. 

All in all, basic math would suggest that rather than buying equipment parts, crafting equipment and equipping my troops, I should rather buy advanced resources and just train more troops. Or, if we're not talking about buying them on the market, I should sell my harversted resources (like Giant Rat Furs) and with the gold buy advanced resources for more troops. Or even better, use my harvested resources to create items, sell those, instead of equipping my troops and then buy items to create more troops.

Now, I suspect the two main factors in this are the duration time to train troops and the upkeep. Obviously instead of waiting to train 10k spears, I could only train 5k and craft another 5k Plainsman's Armour and then when using them on Plains have the equivalent of 10k spears with half the upkeep and half the training time. 

But is it really worth it to spend the equivalent of 11 spear units in gold on a single unit that acts like 2 on plains? As mentioned early in the post, I don't have practical experience, just theoretical knowledge, and that's why I'm posting here. I wonder exactly how useful that equipment is for the troops? Is it worth it to hoard it in case there's a war or rather hoard advanced equipment and hope that I can train enough troops when the time comes? Or just hoard troops despite their upkeep so that I'm always ready? Or am I missing something about war equipment that makes it a lot cheaper or a lot more useful?