Armor pricing and AC in the PHB has always bugged me. What's bugged me most is Splint mail. It weighs exactly the same as chain mail, offers better protection, and only costs 5 gp more. Why on earth would any warrior in his right mind ever choose chain mail? If he only has 79 gp to spend, he's better off getting a suit of hide armor, a shield, and better weapons than his measly 4 gp would normally allow. I also didn't want to overly complicate things as I do want to introduce this into a rules light version of the game.
So how do I make armor pricing make a bit more sense?
I already track wounds. This is because I allow bandages to heal 1 hit point for each wound taken in a combat. Heck, I even record the type of damage as some wounds require a poultice or splints in addition to bandages. So the easiest way I could think of doing this is that for each wound a character takes, the armor takes a point of damage as well. When armor takes enough points of damage, it degrades 1 AC level. A skilled armorer can, for a fee, repair the damage. Assuming the character has not let it get to loss of AC, any warrior or cleric can repair the damaged armor themselves with the appropriate tools and a little bit of time(armor repair kits finally coming in handy for more than just the armor polish). In addition, this system allows for disreputable dealers to sell "slightly used" armor at normal price using a bit of polish to hide the dings. To counter this, Fighters(and only fighters) should be able to judge the actual quality of armor. For the purpose of this system, magical armors are impervious to this type of damage.
I divided the armors in the PHB into 2 groupings: material and quality. Material is based on what I have read about the composition of the armor and how it was supposed to defend the wearer. The two materials are Cloth and Metal. Quality determines the number of points the armor can take before it loses an AC point.
The Qualities are: Bad 5, Poor 10, Average 15, Good 20, Amazing 25
Padded Armor(AC 8, Bad Cloth, 4 GP)
Leather Armor(AC 8, Best Cloth, 5 GP)
Ring Mail(AC 7, Good Cloth, 100 GP)
Studded Leather(AC 7, Average Cloth, 20 GP)
Brigandine(AC 6, Average Metal, 120 GP)
Hide Armor(AC 6, Poor Cloth, 15 GP)
Scale Mail(AC 6, Average Metal, 120 GP)
Chain Mail(AC 5, Best Metal, 75 GP)
Banded Mail(AC 4, Average Metal, 200 GP)
Splint Mail(AC 4, Poor Metal, 80 GP)
Bronze Plate Mail(AC 4, Good Metal, 400 GP)
Plate Mail(AC 3, Good Metal, 600 GP)
Field Plate(AC 2, Good Metal, 2,000 GP)
Full Plate(AC 1, Best Metal, 4,000+ GP)