Chch to Auckland is a pretty standard run for them i spose, to get the same tank to say Rotorua is over double.
You can take a look here if you want, this is just the Fliway m2 rate worked out on some standard size tanks to a few places around NZ.
http://www.insideoceans.co.nz/Links/frieght.jpg
I sould also add this is without the fuel sercharge of about 5% i think at the moment.