Those prices Mark.C has them listed for are ridiculous! Only someone who really needed/wanted an Aussie set would spend that much
Most likely due to economy of scale though. If they could be made cheaply in a large batch, I'm sure many of us would buy them to have Aussie only coin entry plates on our doors. Once the price nears Mark.C's, I'd stick with what I had, unless they were badly burnt, have big holes in them or missing altogether.
Not trying to be negative, just wanting to voice my opinion.