According to Fast Company magazine and a study by MIT, paying people to be creative or productive is often counter productive.
The MIT study offered three levels of monetary incentive correlating to the level of success. When the system was tested against menial, mechanical tasks the incentives worked exceptionally well.
However, once even even a slight amount of cognition was needed, the larger the reward the worse the participants performed. This has been tested over and over. The findings the same, every time.
Now the lesson here is not to stop rewarding creative tasks financially. The idea here is to inspire you to search outside your payroll and equity holders for creative input once in a while.
Your customers are not paid to be visionary.
Instead, ask them early in the process and pull together contextual information to properly evaluate their input.