Opportunity cost at Google

The New York Times has an article about how Google decides when to kill a product. I liked this sentence:

With services that don’t generate much cash, the company looks less at money spent than at measures of usefulness and the opportunity cost of devoting employees to one project over another.

Elementary economics stresses that cost is not money spent--cost is what the people and resources that are developing the product could be doing elsewhere. Cutting through all the exposition, Google uses a cost-benefit approach to managing its business.