Wholesalers and item descriptions

I was looking through potential wholesalers on a few sites and some use unit which makes sense for a price per unit but some will say carton and box. box does show how many units it holds which makes sense but some are charging per carton but the only description i get is a units per export carton is equal to like 500. Is the price per carton = to price per unit or is it actually just a metric butt-load of product they are offering?