I've never seen less than 1.5$ per key. Your chances are low but good luck.
He's asking himself "why not have a try at this thread" even though he already knows the outcome.
I think there are better business opportunities than the same old Steam key selling business.
I wasn't really interested in prefacing this with my experience in the RMT industry, but for the last 10 years I've ran and expanded a company that provides goods and services to MMO gamers. WoW gold, Diablo gold, Even isk, etc. Entirely vertical (to the best of our ability) , fully staffed, and properly marketed online.
With that said, this was simply a move into a growing market (CS:GO). To say that keys under $1.50 are carded is speculation, and I would rather assume that the person figured out how to duplicate the keys, or various other legal mechanics to accumulate bulk keys.
If someone is interested in a very organized, and profitable business opportunity, send a PM.
Either way, have a great night everyone and thanks for your replies.