"high fructose" corn syrup--what's typically used to replace sucrose--is 55% fructose, not 100% fructose. IOW, only 5% more fructose. (It can even be less than sucrose, as low as 42%, but for sake of argument 55% seems fair.)
~55%, plus another 50% of the sucrose content once its broken down in the gut, which means it's effectively somewhere around 75% sucrose for the body to break down~
EDIT: nevermind, assumed the rest was sucrose rather than glucose
