Something that seems to be the case across the board in #steemmonsters is that the price of the packs is far more than the cost of the cards on the open market.
For example there are epics in alpha that are going for under $0.50.
I know if you get a pack then foils and legendaries become a bit more valuable but realistically you can get a self made pack of cards of your choosing in alpha not the current beta that could be 4 random rares and one epic and you'll still be paying less than the price of half of a pack.
Let's be realistic too if you want a particular alpha legendary they're still cheaper to buy than 3 packs of beta, and odds are you would never get enough to sell on the open market out of those packs to be able to buy the legendary you're looking for.
At the end of the day this is going to be a game, and when that goes live perhaps these prices will shift around to better reflect their rarity, but for now I think the only way to go is buy whatever cards you want on the open market.
For now, I'm still expecting prices to drop slightly as more betas become available then perhaps a rise when the beta packs sell out.