(Credit: CNET Australia)

UPDATEDThe only thing that can jeopardise your post-iPhone purchase buzz is knowing that your friends bought it cheaper through a rival operator.

It was apparent from last year's pricing that when buying the iPhone, more than any other phone, it's important to understand your usage. Do you need $1000 worth of call credit? Will you use 1GB of data? The operators prey on this uncertainty with plenty of leeway to upsell customers who don't know the best usage plans to suit their needs.

Cheapest "$0" upfront price — 32GB 3GS

Browse the available iPhone 3GS (32GB) plans.

*The Optus 1.5GB data is a bonus when taking a new contract. After the contract expires customers will have to pay $14.99 per month for 1GB of data.

Cheapest "$0" upfront price — 16GB 3GS

Browse the available Apple iPhone 3GS (16GB) plans.

*Updated Optus 16GB pricing as of 26 June 2009.

Cheapest "$0" upfront price — 8GB 3G

Browse the available Apple iPhone 3G (8GB) plans.

As you can see by all the asterisks above, it's certainly — some might say deliberately — difficult to decipher the carrier's iPhone plans. At around the $100 per month mark Optus comes in marginally cheaper, but only because of the bundled data bonus. Optus updated its 16GB on launch day, though Vodafone still wins in the mid-range on a straight out-of-pocket expense basis (though Optus includes considerably more calling credit), and both Optus and Vodafone are matched at the 8GB price point.

Telstra offers numerous plans for iPhone customers, but only one plan comes close to the offerings of the competition. Telstra call it the iPhone Plan Ultimate, and for $150 per month you get a fully subsidised phone plus $1500 worth of calls and 150MB of data. All of Telstra's plans can be extended by adding a data pack, starting from $5 for 5MB ($1 per MB excess usage) through to $119 for 9GB ($0.25 per MB excess usage).

Each carrier also offers several lower cost plans that include monthly handset repayments. For a full list visit each company's website.

Internet tethering

This section really only applies to Optus as Vodafone announced it will not charge extra for iPhone tethering functionality. Optus has a $9.99 per month cost to use your phone as a modem, but for a limited time will waive the cost for customers who take an internet data add-on pack for the same amount or more per month. This includes the Timeless plans which include bundled data.