How can ordinary people challenge patent registrations in a fair way? It is easy to claim that a solution is trivial, but it is almost impossible to prove that if you know the solution already.

Feel free to adapt the sums I listed, that would not change the procedure. I do think that there should be a decent financial burden to protect an idea though. If your idea is good, you can still borrow money (or split patent revenue with investors).

Yes, I suppose my judgment was too harsh, sorry - I don't have a better solution, I just think it's an extremely difficult problem, perhaps not one that's solvable in a financial system like what exists today.