Yes I do. Maybe even more. When I evaluate challenges for our company I do actually spend a lot more time going through the challenge then what it took me to solve it myself and I am not the only one evaluating each one. We also got a lot of feedback that our "estimation" of how long this challenge takes is very accurate, so I assume they take roughly the same amount of time that it took me to do it.
I don't think it is wasting time. Even with the very simple challenge we give out we are always surprised at the wide variety of solutions we get. We found it very useful in our hiring process.
Of course that is just us, but when I was on the other side the people evaluating me where asking detailed questions about my solution more often then not. So I assume it is fairly common that the companies actually do also spend a lot of time on each challenge.
