I am not sure if I can name the website and user in place so if it is allowed I will. I thought reporting this is important since this website is being used as fake advertisement by them.
The way this is set up is by having 2 different deals available for a game. 1 normal key and 1 gift key. The gift key is much cheaper than the normal key and this is the fake deal. This gets immediately deleted when you want to purchase it. Then the only thing left is the more expensive normal key. Then after 24 hours this key will get a small price cut. And another 24 hours it will reset back to how it was originally.
I have contacted the website in question but they just told me "prices change".
I don't know fully why this is done but it seems like a rather scammy way to get people to sign up since that is required to buy. And after they signed up, people might be more likely to buy there anyway.