I think there's a little confusion here about the cost of making biodiesel vs. ethanol.
Making biodiesel or WVO from free used cooking oil is very cheap. $1/gal?
Making the un-used cooking oil is much more expensive.
If you had to make the oil from raw products, then refine it to biodiesel, then it would be $8+/gal.
To answer the OP's question about MPG and biodiesel; yes, it's not as good as petro diesel. I've seen 1-5% worse and 4-10% worse. Lots of variables there. I've been running B100 for 6 months now and B99 for 2 years before that and my driving style blocks any good study, but the difference is marginal. I know marginal is what hypermiling is all about, but once I started making my own fuel, I cared less about MPG and more about that cool smell that followed my truck around.
-Kevin