Gas has been steady at around $3.47 for low octane blend.
A few years ago at the lake, they sold the the 104 stuff for around $5-7 per gallon, when pump gas was around $2.00 at the lake.
Mercury Marine sells a 1,350 hp engine, with a one year warranty that runs on 91 octane. Don't know the price, but I bet it's way north of $100,000. 552 cid and around 6,500 rpm.