Maybe there could be some "high score" list, showcasing the people who have contributed the most, and also have given a high ratio of Like-vote-upvoted feedback. Then people might want to contribute, and include the high-score-presence in their resume / online portfolio.

Or maybe some people to via sth like Patreon would want to pay talented people in low-living-cost-countries, to spend some of their time at Usability Testing Exchange, helping others.

Do you have any thoughts about this or additional ideas? :- )