How much is a fair price for reinforcing armor?

[animewatcha]

In 3rd edition dragon magazine. For a sizeable amount of money added onto original cost, you could add either +1 to the armor class or up the max dexterity by 1 (segmented).

For 5e, what would be a fair price to add into the 3 armor types for the +1 armor class reinforcement or the segmented (medium and heavy) to up the max dexterity by 1?

[diplomancer]

About 30,000 GP for Plate, going by the current progression. 200/75=2.67; 1500/200=7.5; 7.5/2.67=2.81; 2.81×7.5×1500~31,612.5 round that down to 30,000.

Or if you want to make it simpler, just compare it to the magic item costs, as those are functionally magic (+1) armors.

[Anymage]

3.5 was designed with stacking bonuses in mind. 5e very pointedly was not. I'd be inclined to treat such things as magical bonuses and price accordingly. And definitely wouldn't want to let reinforcement bonuses stack with magic, since that gets us back to stacking bonuses in a system that's not built to expect them.

[JackPhoenix]

Let's see... +1 armor (which is what the suggestion is) is rare item, which, per XGtE prices, is worth about 11k gp (2d10*1000 gp). +2 armor (for both improvements) is very rare, which would be 35k gp (1d4+1*10 000 gp).

[stoutstien]

Id use Damage reduction for this not AC. Way less jarring on the curve and easier to add for a reasonable price.