Why is premium gasoline SO much more expensive?

I realize that the current thinking that most cars do not even need premium gasoline since performance is only marginally impacted with its use. But I recall that in the not-too-distant past premium would be something like $ 0.20 more than regular. When I went to the gas station over the weekend I noticed regular gas at $ 3.89/gallon (hey I live in very expensive Connecticut) and Premium was $ 4.37/gallon. That's almost $ 0.50/gallon more! What gives?

I tried to remember that when gas was $ 2.50/gallon (not all that long ago) premium was $ 2.70 (or thereabout). Less than a 10% premium for premium. But today it is close to 13%. Since it weighs the same the delivery cost should be the same. Can the refining of gasoline to 92 or 93 octane vs. 87 octane really be worth $ 0.50/gallon? Or are the oil companies trying to get us to give it up entirely (my view). It has to be easier for the oil companies to have only one type of gasoline to inventory and deliver. I see 'plus' gasoline going first and then premium slowly will be less and less available.

So we now live in a world that in contrast to what one would think, has situations where fewer choices reign instead of more choices. Maybe the scam all along was that premium gas was never needed in the first place. But both of my cars have lettering saying 'Premium gasoline only'. I kind of like being defiant when I put in that regular gas! But I still would like to have a choice...