Item cost element
It would be beneficial for us as a business keeping track of finances, by having another field in products like hosting, domains etc where you can enter a cost for that item. Domains cost $9, you sell for 100 $15, WHMCS generates a report saying your income is $1500. this is not accurate. as you sell various domains and hosting items with a varying cost associated with each, accounting gets pretty tedious.
This is especially useful when a WHMCS user is reselling services from a 3rd party as each item has a fixed cost price.