I open 3 - 4 boxes per set so I really do not buy alot of cards for decks. Some cards I have to buy (like staples, luxrays, etc).
My flygon deck has 100-150 in cards in it. The staples cost 30 - 40 per deck for most decks if you buy them. (Rosannes (20), Bebes (5), Communicator (12), Rare...