"The trucks from port to mine are supposed to be empty!" - hence...

"The trucks from port to mine are supposed to be empty!" - hence it costs more than usual (maybe TOLL realised this after initial negotiations and are now trying to back out). By the way, KLL said that "commercial discussions between Toll and Kalium Lakes on this matter remain ongoing".

My understanding is that KLL were going to get a reduced rate because they were on the "back haul" - ie - someone else had already paid for the forward trip. Now, Toll are saying they don't have enough forward trips to be able to offer the required "back hauls" to KLL.