Been thinking about this myself lately.
I'd say there is definitely an element of gambling involved. More so when there are different levels of value attached to certain cards. I know I've fallen into the mindset once or twice. I find the more you get lost in the re-sale value of a card and the money-making aspect of the hobby, the more it becomes gambling like.
The way I reframe that is to just enjoy the product for what it is, I get a little buzz even when I pull a base card of a big-name player.
Like
@Matt26 has said, it's the group breaks that really ramp up the gambling aspect for me. Where they only send out hits and inserts. You can pay a lot of money and end up with nothing. I've done it, but I might start looking for more breaks that send out base cards as well (anyone know of any local NFL options?)