There are (at least) two kinds of things that are difficult to do:
1) Things we know how to do, but lack the resources to implement
2) Things we don’t know a way of doing.
For example, if I had several billion dollars, I could probably build a duplicate of the Great Pyramid of Egypt. (Modern skyscrapers cost similar amounts to build.) The Apollo program cost about $170 billion in today’s dollars. A manned mission to Mars, including a return trip, would probably be doable if some organization was willing to spend a few hundred billion dollars to do it. (A few hundred billion dollars spent on improving developing world health could also have a huge impact.) These are all difficult things to do, but prizes don’t seem to be a particularly good way of getting them done—if you have the money to spend on them, you can often spend the money on them directly rather than on prizes, and if you don’t have the money to fund them directly, you won’t be able to offer a big enough prize to get someone else to do it.
On the other hand, prizes can certainly be a way of attracting attention to a problem that’s being neglected and that is capable of succumbing to innovation in a way that stacking stone blocks isn’t. There also seem to be problems that don’t seem like they would benefit from having bigger prizes for solving them; would offering a billion dollar prize for a proof of the Riemann Hypothesis get us a proof any faster than the current million dollar prize would? (The person who proved the Poincare conjecture didn’t even accept the million dollars!)
There are (at least) two kinds of things that are difficult to do:
1) Things we know how to do, but lack the resources to implement 2) Things we don’t know a way of doing.
For example, if I had several billion dollars, I could probably build a duplicate of the Great Pyramid of Egypt. (Modern skyscrapers cost similar amounts to build.) The Apollo program cost about $170 billion in today’s dollars. A manned mission to Mars, including a return trip, would probably be doable if some organization was willing to spend a few hundred billion dollars to do it. (A few hundred billion dollars spent on improving developing world health could also have a huge impact.) These are all difficult things to do, but prizes don’t seem to be a particularly good way of getting them done—if you have the money to spend on them, you can often spend the money on them directly rather than on prizes, and if you don’t have the money to fund them directly, you won’t be able to offer a big enough prize to get someone else to do it.
On the other hand, prizes can certainly be a way of attracting attention to a problem that’s being neglected and that is capable of succumbing to innovation in a way that stacking stone blocks isn’t. There also seem to be problems that don’t seem like they would benefit from having bigger prizes for solving them; would offering a billion dollar prize for a proof of the Riemann Hypothesis get us a proof any faster than the current million dollar prize would? (The person who proved the Poincare conjecture didn’t even accept the million dollars!)