I had to buy a new greenslip for my motorbike this week.  My motorbike is a Yamaha XT 600, a single cylinder trail bike.
I did a price comparison and found the results very interesting.
The cheapest greenslip price was $424.00 and the most expensive was $686.00, a difference of $262.00 or 61.8%. 

As a Ulysses member I also obtained a quote from Monalnd Pty Ltd.  They sell CIC Allianz greenslips to Ulysses members under a fleet arrangement.  Their price for a CIC Allianz greenslip was $383.00, a further saving of $41.00.  I purchased my greenslip through Monaland Pty Ltd.

Incidentally, the MCIS Levy represents 30.4% of the cost of my greenslip.

Clearly, if price is a determining factor in your greenslip purchase, it is worth the effort to do a price comparison and to understand your options.