Not only does that value let players cash out to some extent, it limits the amount 'whales' will commit to the game. Good Magic decks range from "not cheap" to

Not only does that value let players cash out to some extent, it limits the amount 'whales' will commit to the game. Good Magic decks range from "not cheap" to "breathtakingly expensive", but no one assembles tournament-level decks purely from opening packs; they buy at least some of the cards from aftermarket sellers. That's a fixed price for a known good, which gives some confidence that people are making rational buying decisions even when they spend a huge amount. Even casual players are quite likely to open packs, find some things they want to build around, and then fill out what they need by trading or buying. It offers a backstop on the entire system that digital and especially non-transferable products simply don't have.