It is as simple and direct as possible for the desired outcome. Sometimes a seemingly impractical solution is actually only a communication problem. Many new Internet companies, for example, seem unable to explain in a few, clear words, just what they do. The solution will continue to work over time with a high degree of reliability, consistency, and effectiveness. It still works.
Dependability is at the core of user satisfaction.
The parts cost may be trivial, but replacement cost in labor, disruption, and psychic trauma add up quickly. Or if the matches are great when they light, but they don't always light. . . . The solution is innovative, breaking new ground. A ball point pen with a particularly great design may be seen as original from a design point of view. The solution is unusual, out of the ordinary lines of thought.