Well it’s dodgy because it IS dodgy. From £50 to £42, it’s not a huge sale. I even bought it 40€ instead of 50€ myself, on a website I know is trustworthy. But 25€ ? 50% sale on a game that is barely just out? Come on, it’s just too good to be true.
My take on this is that the dev actually get nothing from the sale. The key was obtained via unknown means, either stolen, via a free promotionnal operation, or something that inevitably will result in the developper not getting the money, and the reseller getting it all. You may very well be well meaning, but in trying to save a few bucks you denied the real authors theirs, and rather further contributed to make this kind of despicable websites continue running.
What’s even more sad is that the small studios will be affected the most. Getting a Call of Duty key won’t really hurt Activision. Getting a Battleborn or a indie game key, though, will probably not help the game.
I can only beg people not to use these sites. Use real, official ways. Think not only with your own wallet and the couple buck you will keep. Heck, I’d encourage piracy before using those sites. At least with piracy there is a chance you would go and grab the game “for real”, resulting in GBX getting some money for sure, whereas if you acquired the game via shady means you won’t buy it a second time… ( kay battleborn probably can’t be cracked because of the whole MP aspect, but I hope you get my point ).
edit : as far as operating goes, I can only urge you to read the link I posted earlier. They aren’t culprit. They operate by collecting keys people sell them. It’s a chain, but almost inevitably you will find out there was one loosy link, and at some point, someone lied about the origin of the key. The people that manage the site won’t look, and chances are the customers won’t look either. At any rate, the key is mostly perfectly valid, but chances are that this key should never have been sold in the first place. You know, this kind of product which come with a little disclaimer : " this product shouldn’t be sold separatly ".
That, or using massive bulk sell at a hugely discounted prices in one country and then use the power of money conversion to get it to other countries for half the price it should have costed there.