Think there is something wrong with your prices. I suspect your source might be biased and question the validity. In Tennessee, where I buy my eggs, a dozen is over $2 and has been for some time. TN is supposed to be a cheap state.
Also, and my real point, mcdonalds, and any other company in America, pays a lot more for the services of their employees than their wages might suggest.
I would be interested to know what the cost of employment is in Australia compared to these united states. Your average hourly employee costs a business about twice the amount they actually pay them. The government requires employers to keep up several different kinds of insurance for employees, and they only charge the employee half of the FICA taxes, the employer pays the other half...
In Australia it might be very different, although it would appear that the minimum wage worker in Australia is better situated, perhaps their employers are too.
My point is only this though, given all the complex variables, it is fundamentally dishonest, or very ignorant of you, to simply say min wage there is a lot higher, but the big Mac costs the same. There is very likely a lot of other things going on.