From the german chaos computer clubs yearly meeting. Linus talks about what to do and who ransoms work, how "well" the service is and briefly pros and cons of paying.
https://media.ccc.de/v/37c3-12134-hirne_hacken_hackback_edit...
Also a good one was the first part: https://media.ccc.de/v/36c3-11175-hirne_hacken
To puff and look important and to say
Though we know we should defeat you
We have not the time to beat you
We will therefore give you cash to go away
And that is called paying the Dane-Geld
And we've proved it again and again
That if once you have paid him the Dane-Geld
You never get rid of the Dane
Somewhere I read that some ransomware had excellent "customer" service for helping you transfer over the payment and promptly restore your files.
From their side, the logic seems as simple as: repeat the attack -> some chance of more money, don't repeat the attack -> 0% chance of more money