If you really wanted to start getting into the cost per item (when did D&D players turn into interior decorators...?), you should probably look at the base prices for items that are listed in the PHB (a chest comes to mind: 2gp), find out how much the equivilent costs in the real world (for a basic variety of it), and then estimate 1gp = X dollars. Some things you could probably go off of, as well: a crowbar, chain (10ft), a ladder (10ft: keep in mind this is just a standard, straight ladder, no folding or collapsing at all), an iron pot, a sledge hammer, etc.
Obviously, there's going to be a variation in the price due to economic issues:
"Light horse" (Arabian): $750 = 75 gp = $10 per 1 gp
Crowbar: $16 = 2gp = $8 per 1 gp
Iron Pot: If you can find a simple, iron pot, you're lucky
In the end, just go with what feels like an adequate cost per item.