That's expensive!
$6.79 a gallon.

When I went flying with my friend we gassed up his little kit plane that has a modified VW 4 cylinder engine and I saw an AVGas pump rating of 100 Octane.
Moreover, it was a lot cheaper than $6 a gallon. As I recall it was about $3.99 in June when I was paying $2.86-$3.47 for regular unleaded 85~87 Octane.