I think I am somewhere between $600 and $750 for each of my cars (it would be cheaper if the convertor of my Corvette put the correct weight down on the paperwork when they rego'd it...:20). Have to get a blue slip change of records to rectify it... :20
If you want personal plates like yours I think it is $400 per year on top of your normal rego costs (and there is a fee to make the plates up too).