Every card has an equal 20 percent chance to be chosen, but the cost of picking from a pack varies depending on the rarity of the cards it selects from
For your collection
Officially licensed 100ct Sleeves for Magic: The Gathering Commander Masters 107 standard size Deck Protector sleeves in each pack Matte finish with ChromaFusion Technology to prevent peeling Features exclusive artwork for MTG Deck protector sleeves, standard size card protection sleeves
A full booster box, which has 24 packs plus a box topper - which can itself be good or bad, depending on your luck - will cost you around 260
Tome is strong at introducing some fun card drawing to the build
And even if you don't go crazy, sac a bunch of tokens, get a bunch of Blood Artist triggers, and what have you, you can still easily end up with a pretty big flyer for four mana or give/proliferate it counters through other means