My name is familiar? Hmmm...either it's from here several years ago...or some 15-odd sites many years ago...or it's from Syndrone, Avaricia, or possibly Menewsha fairly recently...
The trouble with that idea, though, is if you can buy the commons with Aurum and Runes, it's essentially an "aurum generator", where someone can pay to make more aurum.
If you ever go to Gaia, you can see exactly what happens when you allow that. Specifically, crazy, mind-bogglingly high inflation.
So, unfortunately, we will not ever allow the buying of aurum items with Runes.
That said, I'm sure you can easily trade with other users to get the aurum you need. :)