Note: This will be a contrived example, but hopefully illustrates some real-world trade-offs.
Example scenario: Suppose you're an independent web developer, and a client asks you to prototype a redesign of their website header. You'll be paid for your time, and if the client likes it, you'll be hired to do the full implementation. Your incentive is to show the client a quick, functional demo of the updated header. The problem is that quick and functional tend to be mutually-exclusive.