I don't know if this is the best place to talk about this, because isn't really a Support question. In fact, is more an idea for improvement of Ads Manager:

Maybe it would be a good idea to have the possibility of use social shares as credits. For instance: I want to create a complete free access directory, with no money fees; but, on the other hand, I want users contribution by sharing on facebook or twitter.
So, if there's a way of create credits with socialshare, it would be fantastic!

All the best.

In the meanwhile, I think it's possible to have a similar result using the actual params of the component.
Let's suppose we want to give 100 points for each tweet or FB share. We can create an 100% discount cuppon, hidden in the website (for example with a plugin like Pay With Social ) in order that users who share the website get the code, and with the code they get points to extend their subscriptions and/or promote their ads.
Is not exactly what I have I mind, but it may work, I think.

I'm working on it, let's see what's happening.
Is there any option to ONLY have payments in credits, and not in any currency?
And, in that case, what will be shown at the form (tax, unit price, etc)?
Tks