yes but there's a problem there. To make it worthwhile, you would have to pay for it by mining even rarer blocks, which would take just as long if not longer due to the lack of them. The other way is for gar to sell track at a very low price as you say, but that does seem to go against the idea of playing this game the way its meant to be played.
It's off on a tangent anyway. but it does demonstrate how unbalanced the minecraft world is, currently, and how i believe in this state i just dont think it's worth the effort to either stamp out duping or start over yet again.
Or you could bulk sell farmable things, like wheat or leather/pig meat/bows and arrows, silk and gunpowder.
After a reasonable investment of time and energy you'd have a nice steady income.