You can record the purchase price on quotes/invoices on a line-by-line basis

Currently, this is a read-only column where the purchase price is retrieved from the rates. However, the purchase price may differ now from what it will be in, say, a year.

In addition, there are cases—such as quote rules—where the rate (one-time) isn’t listed under Basic Info -> Rates; in those cases, it’s also useful to be able to enter a purchase price there.