Well, if you've got rich friends, you could end up legit getting S4's SPs free too through gifting on Origin or gift codes from places like Amazon. :D Not to mention there are regular sales (though not so often for SPs I guess).
Edit/Addition: If anyone's interested, let's say the average amount of items in a S4 SP is around 40. (I think it tends to be a bit more, but there may be a few packs with less, so again, let's just average.)
$10.00/40 items in the pack = $0.25 per item. It's less than that if the pack has, say 50 items ($0.20), and a little more if it has, say 35 (roughly $0.29).
Again, I have no idea how many items were in a $20 pack on the S3 Store to figure out that amount, but those of you with that experience can do the comparisons if you're interested. This is the only way I can figure to compare actual monetary value of the packs without subjective things like preferences for art style/game/etc.
