I think you're right about this as well. From my perspective, I spent a little to get started, but now I don't envision myself ever needing to spend money again, the gold payouts are just so generous for a casual player who plays 5-10 games a day (which I still think is a fair amount).
Meanwhile, people are complaining they don't give out enough gold, which I really don't understand, well because I don't play hours and hours of the game a day I guess. If they do ever increase the gold payout by a substantial amount, I hope they add more gold sinks, because otherwise in enough time my reserves will probably hit 5 or 6 figures.
I'm in a similar boat, though I haven't spent any money. I'd actually be willing to pay some money to support the game, but there just doesn't seem to be any reason to. The gold rewards from dailies and Arenas are more than generous enough to build a decent collection without spending too much time.
Of course, some people seem to be approaching the game with an MMO mentality. They want to grind countless hours every day to complete their card collection ASAP, and get frustrated because this tactic isn't effective. The thing is, Blizzard doesn't want players grinding this way. They get no money from these players, it puts additional load of their servers, and once the players complete their collections they'll most likely just complain about having nothing to do before quitting the game. The current payout structure is designed to discourage grinding, not encourage it.