First off, apologies if everyone is familiar with this , but I have been banging my head on the desk trying to get this to work for a while and I thought someone else might be struggling with it 
You can use your postback URL in prosper to get the real payout for each conversion. This is of great use when you are rotating different offers, or you get a pay bump (or pay cut),etc and you need to get the real conversion value so you have real income numbers in your Prosper DB. I'm guessing this should be pretty similar in CPV Lab.
I've only tested this on networks using Cake Marketing and HasOffers.
First, get your postback URL from your Prosper install ( #8 Get Postback/Pixel) :

In HasOffers, go to your offer page and at in the bottom of the page, you should find the Conversion Pixels field. There, you will find a link for all the Tracking Variables you can use. In my case, all I want is the Conversion value and the Subid for tracking:

Don't forget to click Save.
In Cake Marketing networks, go to your offer and in the Testing and Tracking tab you should find what we are looking for. Again, to the left you will find all the tracking variables:

Again, click Save.
Now, every time you get a conversion your Prosper tracking should get the correct conversion value! No more guessing and messing around with Excel sheets.
Remember, you need to do this for each offer in HasOffers and Cake. I'm not aware if they have a Global tracking pixel.
The only thing that's left for me to figure out is a way to get real Ad costs 
Good info man, currently working on setting up my first campain in prosper and I'm sure this info will help me out.