there's a utility cost to refine crude. utility prices go up when cost of hydrocarbon goes up. I just resigned my electric contract recently and my cost went from 12c/kWh up to around 19c/kWh. that said, agree that the other costs should remain fairly constant over time.

That’s correct. That’s why the height of the green bar varies over time.

yes - when price of oil goes up the cost for a refinery goes up for both feedstock and cost of refining. cost of refining will go up because utility costs go up.

Cost of crude represents majority of refinery costs.

Refineries purchase crude on open market. Crude price function of supply and demand.

Profit margin equals revenue minus expenses. The above plot shows only expenses.

The market

Crude costs fluctuate because price of crude is based on supply and demand

Refineries have to purchase crude oil.