Item pack economy?

There's not enough information yet, but from what I experienced the packs have a rarity: common/uncommon/rare/ultra-rare.

Each pack have 5 cards where 1 (guaranteed) or 2 (if you're lucky) of them are of the specified rarity and the rest are fillers like ammo, revive packs, etc.

Given that each pack gives you a small chance to get a hier rarity card, example the basic pack gives you a small chance to get 1 uncommon, if you really want to optimize you buying you should buy the lowest pack possible until all commons are maxed (level X).

We still don't know if buying the biggest pack can give you a common card or not, at least I've heard nothing about it. Although, I'm confident the packs are not as bad as ME3 were (nothing like spending 100K credits on a premium specter pack to get 2 commons because you haven't unlocked them all). So to be clear, I don't think MEA packs will give you lower rarity cards but I could easily be proven wrong, take it as a possibility.

The packs are priced at 500 credits more than the difficulty. What the hell does that mean? The lower pack is "Basic" and cost 5000. Extracting on Bronze (lowest difficulty) gives you 5500 credits (500 more than the pack would cost). This way, you always get "more" than 1 pack per game. Silver games will give you 500 more credits than a Advanced pack and so on. It's actually a good thing, you never get left with no consumables unless you really suck at this game.

I've seen you can buy more specific stuff in the store. I haven't checked that enough to know exactly how it works, but from what I could see the days of having 255 of everything BUT the thing you use are over.

I'm curious to find out some hard data on this as well but until proved otherwise, I'm just going to assume it follows what ME3 did...

Well, ME MP definitely has a tier system. So theoretically if you had a method of being able to consistently buy the top pack without being a cancer to the community, that would be the best choice. In terms of power, rare cards, be they weapons or classes typically have way more power than their common or even uncommon counterparts. For example, I think I got my Viper to something like V? VI? Then in the last pack I opened before my trial ended I got some UR sniper called Naladen or something. It was semi auto, had 4 shots and fired explosive rounds that did more damage at rank I than the Viper would ever do at rank X. It felt like the ME:A Khrysae.

Because the higher packs guarantee rares, they offer more in terms of pure power than the other packs up to a certain point.

I'm rly triggered by the fact that 5000 pack and 50000 pack give you same amount of consumables - 1 per card. Like wtf is this, in me3mp spectre and premium spectre give you 5 consumables per card.

Given the large level up grind, I really feel like they looked at rockstars cash mountain and lowered the drop rates for the best tier stuff. I'd expect maybe 2.5-5% now.