Armor in BX DnD is hella cheap. Why? Because it's old and crappy.
On any successful hit against a PC that does 6+ damage the player must roll a D6 and subtract that amount from the damage but also loose that many points of AC.
Armor can be repaired. It costs half as much as getting new armor.
Fancy/very well made armor can be found, sure. Doubling the cost raises the amount of damage that triggers a break by 1. Like this:
ARMOR
|
Cost
|
||
Damage to Break
|
Leather
|
Chain
|
Plate
|
6+
|
20
|
40
|
60
|
7+
|
40
|
80
|
120
|
8+
|
80
|
160
|
240
|
9+
|
160
|
320
|
480
|
10+
|
320
|
640
|
960
|
11+
|
640
|
1280
|
1920
|
12+
|
1280
|
2560
|
3840
|
I like this because when making a character it doesn't change any thing. Armor costs what it says in the book, there's no weird rule to teach the Players. Then on the second or third session when the ogre hits one of your Players with his spiked war club and does 9 damage you can be like, "that's 9 damage, are you dead? yeah, shoot. oh wait, roll to see if your armor is busted instead." They'll be delighted, and then later you'll get to make up a funny voice for the armorsmith in the next town.