The average hacker has no business sense. He isn't even aware that he lacks one. His world is megabytes and milliseconds, not dollars and cents. He likely has never had a management course—perhaps has never had any kind of business course whatsoever. He evaluates things by their performance and their technical excellence. He may tend to overlook the user; usability and user-friendliness, good online help and good documentation are not usually highest on his list of priorities. Even farther over his horizon is "the bottom line" itself. He is buried so far in the internals that he is unaware of any positive or negative economic impact his actions have.
So here is Tip 1: Remind the developer that technical excellence is no guarantee of success.