Starting on page 175. Goes until 187 or so. You aren't going to see a chart or anything that says "Armor cost = this," or anything like that. Page 180 has some miscellaneous numbers that are special cases, but for the most part, if you're repairing the item, there doesn't seem to be much of a cost. Replacing an item will cost whatever the item normally costs.
So if you're replacing a ton of armor, then your cost is going to be whatever the cost of 1 ton of armor is going to be (you can get the per point cost by dividing the cost by the number of points the armor provides).