Here's how you find 50% savings. Your math was wrong, there was no error. Take the following example:
$10 for 10 units = $1 for 1 unit
An ethanol yield increase of 30% output would now mean $10 for 13 units. Drying gas cost savings of 35% would now mean $6.50 for 13 units.
$6.50 for 13 units = $1 for 2 units
note: One thing to keep in mind is that USSE's process seems to work most efficiently w/ a method that would increase output maximization rather than just cost savings alone.