The national average difference between premium and regular pump fuel is 30 cents. So @junkyardhero statement holds up. In “most” places a tank of premium vs a tank of regular will average about $6.00 not enough to worry about.
see! see! i am capable of level headed conversation and reasonable thought!
my feeling is, if it's costing more than about 1/4 tank to run premium or an additive then it's time to rethink strategy. but if you're putting on sub 5K miles a year and need premium, the cost per tank should be way down on the "concerns" list.