Mere difficulty of a problem does not make those who do solve it a natural monopoly. Of course these player may still be a practical (in effect) monopoly due to

Mere difficulty of a problem does not make those who do solve it a natural monopoly. Of course these player may still be a practical (in effect) monopoly due to their being way better than the competition. Making a kickass image editing application like Adobe Photoshop is difficult too (as anyone who has had to suffer GIMP would attest), but that doesn't mean Photoshop forms a natural monopoly.