I was the one who started that, but I noticed a few times that people are copying it, which is IMHO not a problem. I chose a value that I could use as a measure in how much dumping would occur, that could support the price (and keep it stable) and generate enough order size for merchants to convert back to ISK (although it is now also used for bag holders to cash out). Part of the dumped out AUR are transferred to ISX, initially as a way to transfer AUR back into Iceland, to provide a similar support of the price and again to actually build the support for merchants.

It's all part of building a system to economically support AUR to become a good alternative to ISK.