Most of these sites that email you the key afterwards are shady fly-by-night operations reselling foreign keys. Games in a lot of foreign countries (russia, korea, etc) are priced considerably cheaper even at release for economical reasons, but a lot of them are still either multilingual EU versions, or the standard US english version of the software.
These companies have a hook into some foreign distributor of keys, buy them at a discount, and resell them for less than the US price but more than they payed. You order the key, they buy the key through their back-room distributor, they charge you and email you the key. Easy money, but legally dubious. Of course, if they charge you and dont send you a key, or the key doesnt work, you're typically up shit creek without a paddle, and if it turns out the key was stolen in some way your Steam/Origin/whatever account is gonna get banned.
Not to mention the shady nature of it all means they're probably selling your personal info/credit card info on the side because why not.
These sorts of sites and deals pop up on Slickdeals frequently, the comments typically a mixed bag of "got a key and it works fine," "waited 2 days and never got a key," "its the russian version but it still activates fine and you can set the language to english," "key was bad and they dont return my emails," etc.
Personally, I pay the extra few bucks to know i'm getting legit goods or wait another month for it to go on sale from a real company.
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