That looks like a fad/bubble to me, like when Beanie Babies were going for crazy amounts of money.  The interest (and willingness to spend such outrageous sums of money on trivial things) isn't sustainable IMO.

Coincidentally I was just watching a few documentaries that dealt with these online gaming economies, and I do find it to be fascinating.  I'm not a gamer, so it boggles my mind that people would pay so much money for what amount to cosmetics (if I'm not mistaken).  My mind shouldn't be boggled, however.  I've seen people go crazy for weirder things than CS:GO skins in the course of my lifetime.