I agree. Booster packs should be available to buy with electrum, especially if there are upgraded cards, rare weapons, and nymphs up for grabs. $500 bucks for a nymph? O.o I suppose if you're willing, I can't complain, lol.
I like the idea of booster packs, but I think they should be structure more like real-life booster packs. 1 rare weapon, 1-2 upgraded cards, and the rest random cards, 1 per element, each with a slight chance to be upgraded, and a very small chance to be a nymph. Even with the very high cost, I don't think you should be guaranteed a nymph. Indeed, making something like a .5%-1% chance per card besides the rare and upgraded ones would balance it out since you could by 100 packs and get no nymphs, and people that buy them with electrum (should cost a significantly unbalanced amount, erring highly on the side of too expensive) have a chance to get a nymph as well.
I'm focusing on nymphs here, but if there are upgraded/rare cards, they should cost enough in electrum/money that they're definitely a luxury item, so people with massive amounts of electrum would be better off upgrading cards/grinding to get them than blowing their money on boosters.