A couple of you asked what a "Pin submit" is so here goes. It definitely doesn't have anything to do with Pinterest. They're usually, though not always, a ringtone offer, or some kind of SMS based subscription. As part of the sign up process the user is sent a text message with a 4-6 digit pin usually. They'll then enter that pin on the signup form which completes the verification. Otherwise you could just have a bot with proxies entering manual numbers all day long saying "yeah sure I signed up, here's my number". It's the same as Google's 2-Step auth if you ever set that up where they'll send you a text with a pin code you enter to login. Same thing.
As far as the high payouts go, most ringtone offers dried up here in the USA because of abuse and complaints, but before they did it was not uncommon at all to see a $15-$20 paying ringtone offer. A few changes in the laws over here changed all that though. My guess is that the traffic that those advertisers are seeing in France is converting for them with monthly rebills for the subscriptions that people are signing up for. So if the average user keeps their ringtone plan for 4-6 months, and they're paying let's say $10-$15 per month for it, then it's not hard to see how/why they can offer you $15-$20 per conversion, or even more as someone said above. Their laws are probably rather lax, or not yet in place as over here to squash them yet, so get it while the getting is good, nothing lasts forever