the only way it would be a waste of money is if bitcoins collapse before you mine enough to pay off your card. if we assume that bitcoin will survive for at least the next year you *should* make profit from your card - eventually.
just ballpark figures and napkin math here, but...
lets say for $190 you could get a card that does around 300 MHash/sec (very conservative estimate)
using deepbit's calculator you could expect to make 0.16 BTC per day..
as of right now mtgox has BTC at 13.7 so you would pay off your card in 86.7 days.
p.s. these calculations depend on the price of BTC and the change in difficulty.
p.p.s. I didn't add electricity into the equation. I don't pay for electricity, so I have no idea how much that might add to your costs.
^^ while technically correct, this is probably NOT the line of logic you want to follow. If we all followed this advice, the early adopters (you know, the ones mining hundreds and sometimes thousands of Bitcoins per DAY) should have just shut their machines down and quit mining since it would have taken them 20+ YEARS to pay off their machines.