The opposite of "cost effective"; money spent on projects which ultimately backfire or fail; spending money in an ill-advised manner.
Board Meeting Speaker: People, we need to get back to basics. We need to become thrifty again! So, the board has approved the purchase of new, more environmentally-friendly furniture to replace all of our existing furniture, which we just bought new six months ago. We're going to multi-task by going green and saving green simultaneously. As a side-note...no raises for the next 2 years to help implement our new thrifty phase. Comments anyone?
Sarcastic Attendee: Yeah, sounds very "cost defective" to me!