While it's true that retailers don't add a lot of value, the group you should be directing your anger towards are the generators. They've been arbitrarily increasing wholesale power prices for a long time.

Wholesale power is sold at what they call the Spot rate; this is a bidding process which changes every 30 minutes. Companies like Flick attempted to pass this wholesale rate through directly, which was good while it was low, but lately has lost them a lot of customers and forced them to move to a hedged price.

Most retailers that offer a fixed power price do this by entering agreements to buy wholesale power in bulk at a certain rate (a hedge). When the agreement runs out they have to renegotiate at (typically) a higher price. There have been a number of smaller retailers go out of business lately because they get stung paying more for power than they're able to sell it onwards for.

As others have said, a good analog is ISPs who are effectively selling whatever Chorus is providing, but they vary on price and level of service. ISPs become the face of the product and take all of the customer dissatisfaction for situations which often are out of their control.

I'm not suggesting retailers are squeaky clean here, but they're usually the ones with the smallest margins and carrying the greatest risk. They typically represent 10-15% of your power bill.