The hackers connected to the NotPetya attack are claimed to have surfaced and made demands for 100 bitcoin (~$250,000) to hand over the private key. The demands were made on a Tor site with a message that included a file signed with Petya's private key, so appears legitimate.
https://www.theverge.com/2017/7/5/15922216/petya-notpetya-ransomware-authors-bitcoin-demand-decrypt
There are also reports of them emptying their original bitcoin wallet to the tune of about $10,000.
https://motherboard.vice.com/en_us/article/8xagk4/hackers-connected-to-notpetya-ransomware-surface-online-empty-bitcoin-wallet
That goes against what some analysts were saying that this was "just a destructive malware", and not ransomware.
Seems the reality is a little of both.
Enjoy!
K