It seems the mana cost of pick a card is broken, the first time you pick a card and lock it the cost is 20, then the next time 40, and so on, doubling in cost at each rank up to 120 at rank 5, played two games and this is a definite.

It wasnt, hence my post :S

before, you could spam pick a card with no fear for oom. i think there should still be a mana cost, but the lock should be 1/2 the cast price (so at level 1 lock would cost 10 mana instead of 40).

I think Pick a Card should work normally with the normal mana cost, but there is the option to lock it if you want to pay more mana. This way, you have an option between letting it function the way it did previously, or if you wanted to let it function the way it does now.