Time and time again, Indie Devs have taken to social media time and time again to plead with people to pirate their games than use these grey market sites, citing that they get hit with chargeback fees as grey market sites are often purchased with stolen CCs. Its years-old at this point, but even the BBC reported it on it themselves
https://www.bbc.co.uk/news/technology-48908726 Blizzard famously were deactivating some accounts that redeemed grey market keys in its Shadowlands/Dragonflight era as they were chargebacked due to stolen CCs.
You can of course resort to google to find many accounts of developers' dealings with these grey market sites.
I remember the first time I ever bought from CDkeys... it was Diablo 3 shortly after its release, I had emailed a phone photo of the back of a box with code on show, game blurb all in cyrillic with security tag on the box
Use your noggin, if someone is able to lop 1/3rd of the price off a brand new game, especially if its a Steam key (which it looks like it is for Nioh 3 here), it's for a reason