Not quite. I dont recall retailers raising their prices for winter. The retailer prices are what they determine as the average of high and low throughout the year. If you chose a spot price retailer, you pay the real daily price. The difference is that you can manage the variance or allow the retailer to do that for you
I didn't say they'd raise them for winter, but what they will do is raise them overall when they next can to cover the prices being high with a healthy enough buffer to cover future high prices. What you end up doing as a customer is spread the cost and still pay the retailer extra for risk and profit. Yes you need nerves of steel to ride out the high spot prices, but in the long term you can only win as the retailers a never going to make a loss as they will recoup their costs in the long term.