What I always do when I pay people, is I go back and forth between the two payment pages fiddling with the payment amount, until it's set up so that I'm paying the developer exactly what I said I would, with the FS fee being on top of that, rather than a subtraction from the developer's pay.
Given that offer/payment discrepancy is likely going to be fixed soon, what I'd really like is a checkbox on that first stage of the payment process, offering the option to “Pay worker exactly $XX.XX”, substituting in the payment amount. I think that's the clearest way to express the idea for people, but anything that does the job will work. This will keep the stats clean and accurate, increase revenue by a tiny amount, and make my personal experience on this site a lot more convenient.
DONE / Accepting payments