i play it for 4 months hitting kog the last 3 and i tell you it is very expensive. yes initially you get gems enough to build 3-4 top-tier decks or if you are lucky 6-7 but that's it. at some point you cant build anymore.they dont give you daily gems or the option to craft/trade any card for jewels like they do in hearthstone. so you cant gather the collection or keep up with the meta forever
As a matter of fact pal, I played for the last 6 months and reached the highest rank, and never spent a cent in this game.
And since plenty of people do exactly the same as well, then you argument is pretty much invalid. Maybe it's you the one who struggles a lot in this game. Sorry :o