It expresses two ideas:

• Reduction to incentives is such a useful hammer that it's tempting to think of the world as homo economus nails. Like all simplified models, that can be useful, but it can also be dangerously wrong.
• It isn't very much information to say that people have a price. The real information lies in what that price is. It may be true to say "people are dishonest", but if you want to win, you need to specify which people and how dishonest.