Well, whip out your calculator and start counting. The amount of cards in the game is shown in-game or in various sites. Bronzes always cost 50 dust, silvers 200, gold 800 and legendary 3500.But since there's hundreds of cards so it'd need a real time investment to do it. Though a rough estimation would be couple hundred thousand
Playing since around half through the first set, never spent a single dollar so far. My collection manager estimates that I need ~600 packs on average and 950 packs maximum to finish my collection.
Packs are 100 crystals each and assuming I'd always buy 5000 crystals for $80 this results in $960 average and $1520 maximum cost.