So when trying out the titanium plating upgrade (increases armor durability) for my T-60e model power armor, I noticed something funny about the numbers.
Vanilla T-60e
Limbs: 170 hp
Torso: 680 hp
Titanium Plating T-60e
Limbs: 181 hp
Torso: 724 hp
Percentage increase:
Limbs: 6.5%
Torso: 6.5%
Now lets compare the costs of repairing said pieces and the cost of a negligible upgrade.
T-60e Repair cost
Limbs
6 Steel
1 plastic
1 aluminum
1 circuitry (only for the helmet I think)
Torso
10 Steel
3 plastic
3 aluminum
1 circuitry
T-60e TP Upgrade cost (same for all pieces):
4 Steel
7 Aluminum
5 Adhesive
So, with those resource costs above, I'm going to say it's more expensive to upgrade a piece of power armor to titanium plating. Sure, it uses less steel, especially on the torso because it's a flat upgrade cost, but it requires s a significant investment of aluminum, which is much less common than steel, and https://www.youtube.com/watch?v=Jb5y0uqZUNw. In fact, when fully repairing a suit of armor, it takes 8 aluminum in the process, while the upgrade cost for one piece of titanium plating is 7. The total aluminum cost to full set of T-60e titanium plating would be 42, while the aluminum cost of repairing that full set of armor is 8. Assuming all other resource costs are covered (steel & plastic are pretty common, you only need a mere 2 circuitry and adhesive can be farmed for an unlimited supply), you can fully repair the armor five times for the price of giving it an extra 6.5% of durability. Sure the repair cost doesn't change after the upgrade, so it could be one of those thing that pay off in the long run after repeated repairs, but frankly the percentage increase is so small for such a steep cost, that unless you are wrecking your armor every other battle, you probably won't break even in the expected service life of your armor before you move on to a newer model.
There are the other models and variations to compare, but if i'm going by the https://youtu.be/nBxGvXp8RpA?t=3m29s, all of the armors are roughly proportional. So yeah, you might want to fix that Bethesda.