Mark
I can't remember the exact price of the extra trips, Ben on the editors board might be able to help you, or ring the office they might know.
I did not do the Elba trip, not to good on boats and water...so I spent the free time in the local village and on the sun terrace. I did the other trips and they were worth it...
I work on the theory I might not pass that way again so I see and do all the appeals to me...
It really is a nice little tour not to hectic and a fair amount to see..
Have fun
Cindy