For flailing book retailers, the new Harry Potter tome is like a kiss of life. Potter nerds dressed up in academic gowns and wizard hats queuing up around the block to hand over Real Cash Money. The RRP for the book is $45 (outrageous!), but you don't have to walk far to get a cheaper price. Competition is hot for the dork dollar.

It seems Big W might have taken the game a bit far. It advertised the book for $15 for one day only, with the usual 'while stocks last' type qualification. According to social media some stores had only a box or two of books and sold out soon after opening on said sale day. Hell has no fury like a Potter fan robbed of a cheap read. Big W's Facebook page quickly filled with complaints. News coverage followed.

It's against the law to advertise Harry Potter books (or any other goods or services) at a particular price unless you have reasonable supplies available for a reasonable period. It's called bait advertising and it can be prosecuted as an offence under the Australian Consumer Law. The maximum penalty is $1.1M per contravention.

Whether Big W is headed for Azkaban (or at least a hefty fine) will depend on whether its supplies were reasonable having regard to the nature of the market for the Harry Potter book and the nature of the ad. A 'while stocks last' type qualification isn't a strong defence. You still have to think about consumer expectations for that kind of product.

Maybe people would expect a risk of not snapping up the latest Harry Potter on day 1 of its release, especially if it's heavily discounted. But if Facebook is right (when is it wrong?), then some stores stocked less than 50 books. A risky play by Big W. The negative press and potential ACCC investigation might quickly outweigh the upside of their magical marketing tactic.

We do not disclaim anything about this article. We're quite proud of it really.