Corflute is cheap. There are a few places you can get it from. Bunnings will actually give it to you for free if you ask nicely..lol. They use it in the outdoor tiling section to pack their concrete tiles on.
I bought mine from Modular Plastics from Slacks Creek, $10.00 for about 2M of the stuff. Below is some suppliers that is listed on the ACS website.
There is a company that will deliver it to!
BRISBANE FLUTE SUPPLIES
Address: 56 Pentax Street, Salisbury, QLD, 4107.
Phone: 3276 7933 Fax: 61732767456
Website: http://www.bfsplastics.com.au ( Website also has links to interstate suppliers )
Sign Essentials Pty Ltd
Address: 3/209 Robinson Rd, Geebung QLD 4034
Phone: 61 7 3865 2294 Fax: 61 7 3865 2579
Address: 13 BRENNAN STREET, SLACKS CREEK, QLD
TEL: 3290 3978