Yes, you can track the cost you paid for an item in LIST and see your profit by using the NET PAYOUT in the List Item pop-up window.  There you can enter PRICE, COST, FLOOR, and CEILING.  After entering COST information, the NET PAYOUT information located next to the PRICE field will reduce by your COST, showing your PROFIT.

You can also upload your cost for all items in batch using the url:  More detailed instructions about bulk upload here: