I have pursued this idea.
1) You have to have vast buying power to get a low rate. If you just want a couple million miles, you are not going to get anywhere near 1 cent/mile.
2) The airlines specifically do not want for you to be able to do the above at a low cost. If what you are doing is apparent to an airline, they will shut you down.
3) Many airline partner commercial sites offer airlines miles/points via third parties that manage all of their affiliate/partner offerings. These third parties have agreements to buy miles at less than you could directly from the airlines (quantity buying power) but often require you use their software - all miles issued go through their system. Not easy to game.

IF you have a merchant account that already has $$$$$$ going through it, you can probably earn yourself millions of miles at ~1 cent each by doing something like the below example:
1) Get 10 trusted friends to open a card like the Asiana Amex from Bank of America that earns two miles per $, not one. Friends would open card for your (temporary) use only.
2) Charge $100K to each of these cards over time. Of course, promptly pay the bills to avoid any CC charges beyond your merchant CC fees.

If you have an Amex rate of 2%, that would be 2 million Asiana miles (Star Alliance, redeem alliance wide) for $20,000 in merchant fees. Be aware this sort of thing is probably against your merchant agreement in some way and you will not get away with it if charging 2 million $ is outside of your normal pattern.