Unmarked Grave costs 1 more mana, is sorcery, and is restricted to nonlegendary cards (nice flavor btw), so it's not going into all Graveyard decks, but 2 mana tutor is still a great rate for decks looking to dredge up nonlegendary cards
A lot of balance and care goes into choosing the cost of a card, more than I can express here, but looking for similar effects on existing Magic cards can give you an idea of a fair costfor example, a ramp spell that puts two lands into play ought to cost 4 mana, per Explosive Vegetation
An artifact can have zero charge counters and still happily remain on the battlefield (although usually doing nothing)
A quick overview of the pros and cons: Pros: The simplicity for new players to get into the game and continue playing
Card Sleeves and Boxes Everyone wants to keep their cards safe and protected
Most cards have high-priced showcase and alternate art printings