I'm not sure what kind of abuse of the compensation you are thinking of?
I agree that the most valuable thing is not seeing how the solution was implemented (we want to keep the total hours expended to less than 20 for the senior engineer challenge and less than 5 for the junior challenge) but seeing how someone navigates their environment and how they talk through how they arrived at the solution. It's especially interesting to ask about alternatives, areas for extension and tradeoffs.
I agree that the most valuable thing is not seeing how the solution was implemented (we want to keep the total hours expended to less than 20 for the senior engineer challenge and less than 5 for the junior challenge) but seeing how someone navigates their environment and how they talk through how they arrived at the solution. It's especially interesting to ask about alternatives, areas for extension and tradeoffs.