User blog:Mr.Ages/prices in the underdark

I would really like some input on trade in the underdark. I let my players find a route to a drow city that is looking for surface items.( my mistake ) Now I have to figure out prices for all this stuff. I can't find any basic guidelines for this any where. I don't want to give too much, but I don't want to put them through hell getting there only to have them say "that's it !! that's all we get !!" A 10% mark-up isn't going to cut it. I would really like to know what people think. For example: wooden timbers, honey, fresh fruit. These things must be brought from the surface, with great difficulty, and they are highly prized. The final decision is mine, but I would be greatful if someone give me some ideas. Thanks.