Come to think of it, there aren't much benefits of these kind of gigs, the most you can get is the experience and "feel" . Say if your band is good and really good enough to get those paid gigs/ no-need-sell-tickets gig, you know it yourself that you're good and people are paying to watch you and stuff.
However in this case for P2P gigs, if your band is still not tight yet, I don't see the point of paying and then disgracing your self on stage, moreover if you do badly on that gig, people will remember you to be that sucky band. Not that I'm saying that everyone who attended these kinda gigs are bad.
But if your band is good, you will perform well on stage and people will like your stuff, and you will get opportunities. Its definitely WAY better to spend the money jamming and improve your tightness as a band. The results are much more promising.
Lastly this is what i think, if you've got a shot at something, make sure its the best performance and make it impact-full.
Just my 0.02132134589 cents
Cheers,