Right now, Hearthstone is under fire because people think it's too expensive.

Well, collectible card games are expensive by nature... if I wanted free entertainment I'd stick to Dota or Team Fortress 2. It's posible to play Hearthstone for free but unless you like to lose and fight an uphill battle, a minimum of money is required every expansion to keep on par with the rest of the boys.

This said, I believe you don't need a lot to be competitive... the usual promotion of 50 cards for 50 USD should be enough to make a usable deck and if you wait the meta to settle you can use your dust to craft that one must have legendary with your spare dust.

Right now Hearthstone has 3 expansion per year with no cheaper Adventures (which gave you lots of cards for less money). It's in no way the most expensive hobby out there and for someone like me who play mostly the same games it's actually a wise investment instead of just inflating my backlog with games I won't play.

But honestly, this is hardly very fun. The truth is while you can play Hearhtstone for free or with little money, some decks demand lots of cards and sometimes you just want to try a new, different deck and you may need rare cards you don't have which means more money. I think spending 50 USD per expansion is the minimum, with 100 USD being a more honest number if you want to have a solid collections.

However,  every 50 packs is the price of a new AAA game. I can totally see an old Free 2 Play player getting annoyed he can't keep up anymore.