How are freight costs calculated exactly?

Distance wise , are all routes calculated by the shortest distance around the world, or the distance on the map without going over the edges?

Odd pricing on transports on flour and strawberries

From Nanjing to Kansas City
Strawberry cost $1.00
Freight .18
Flour cost $.60
Freight $1.20
Could we have this looked into? Strawberries are difficult to transport, more so than flour.