Hey dude, its not that your price isnt cheap! You just gotta give us time...
I see Xspeed use these plugs, scroll almost to the end of the page and you will see the cost*
http://www.xspeed.com.au/services.php?area=garage
** Quote from Xspeed page**
· NGK Iridiums - $28.00 per plug
· NGK Iridiums for Rotary Engines - $55.00 per plug
So from looking at that id say your price is damn good mate just double check that you have the correct model.
Also double check the forum rules before selling these items, gotta be carefull bro..