John W, if you wish to play around with the gearing it does pay to go for the quick realease option as standard Ducati Rear Sprocket is as you say £103 or £142 for Ducati Performance. I now have a 36,37,38 and 40 tooth rear sprockets to play around with and luckily for me i had bought these 4 + chain + front 14T for £50 all i had to buy was carrier which was £104.
So worth every penny, But moral for this post is that my loft has loads of spare parts in it also does my garage and i even have a red Complete body kit just for those slow days