I have some detailed calculations. Starship will double the payload capacity. Full fueling costs are about the same for the 1200 tons of fuel for Starship versus 50,000 gallons of jet fuel for a long-range cargo plane for each flight. However, twice payload means half the cost. Non-fuel costs for the vehicles and the frequency of flights are hugely in Starship favor. Starship should have twice the payload.

Starship starts off at half of the loaded cost per flight and four times cheaper per ton of payload and then will proceed to be ten to fifteen times cheaper. Plus they will have some initial new no competition markets for ultra-fast delivery.