I think 4$ is too expensive for packs, yes it helps keep the card count lower, but 2$ a pack is just so much easier to buy for people.
I got even a bit too addicted when packs were 2$ each because throwing down 10$ for 5 packs seems like value, but only getting 2 packs in a 10$ range doesn't give the same amount of fun.
!BBH
I mostly agree, I don't think $4.00 is too expensive more so than the lower $2.00 amount is better for impulse purchases/ overall sales/ attracting new players. $2.00 is low enough that someone can say, alright its just $2.00; lets see what we get in these batch of packs. The fun of opening packs shouldn't be understated. More packs = more fun = happy customers = more sales = so on and so forth. Lowering to $3.00 might even do the trick that way players get 3 packs for under $10.