You can't compare the US price of HFCS to the world price of raw sugar as it doesn't count the absurd US tariffs on it. When you count these in I'm pretty sure that HFCS is cheaper than sugar in the united states.
That's right, HFCS is slightly cheaper than raw sugar in the US because the government has extremely protective import quotas against world priced sugar. The invention of HFCS in the 1980s is a direct result of the U.S. sugar program. But if you allowed a free market for sugar in the U.S. the U.S. raw sugar price would equalize at the world sugar price, and it is likely that HFCS would disappear.