You can now enter an operational cost per rental item that is used along with any vendor cost for a vendor item on a lead to calculate your profit for that lead. To turn this on, you need to add an operational cost to your items. This is found in the advanced section of the inventory item.
To enter cost of a vendor item, you must do it on the lead.
At the bottom of the lead you will see the calculated event's profit based on your cost entries.
This is clearly a simple calculation, but to get a more accurate number, we would need far more input from the users. So it's a good balance between valuable information and ease of use.