I'm on a $19 a month Vodafone prepay. Send a couple of text a month, maybe 20 minutes of calls, and can survive with 500mb data , especially with rollover to cover a heavy usage month.
So I reckon I could pay $10 per month for this, $8 for the data, and the other $2 to cover the text/minutes used. So overall my annual spend goes from 12 x 19 to 12 x 10. $108 saving isnt really that important to me , but I'm sure $108 means more to lots of people.
You could also save $36 per month and be on the same tier network in terms of performance etc, have rollover data etc. Honestly The Warehouse Mobile actually literally makes no sense as a product.