Happens often in PC/console/mobile games when the developers 'suddenly realise' that the skill/ability breaks or unbalances the overall gameplay.
In some ways it is like being baited to get you to buy, then voila, change an important attribute and tough luck, you've done your money. Because this happens mainly with teenagers not many people have paid attention to this 'trick' by game developers. I see it as a type of fraud but don't know enough law to make a comment. In a normal situation you could argue the developer changed an essential element of the contract giving you a right to demand your money back. Not sure if this principle applies in this scenario, and if so, how does Australian law impact overseas developers.
Australian Consumer Law may also apply. Not sure though.
Frustrating but not sure of your legal rights, interested in the answer as well.