WE are travelling in mid september from Venice to Bologna one day, Bologna to Nice the next and 2 weeks later Nice to Paris. It has been hard to put in the destinations and get costs as the schedules are not yet out. Also to connect from Venitmiglia to Nice re times for connections.. any help will be greatly appreciated.
Pay as you go. Venice-Bologne is out now. Lots of 9 euro fares available. Nice-Paris fares are available for as low as 36 euro at en.voyages-sncf.com.
Ventimiglia to Nice is a local train which runs twice an hour. It's cheap; I don't know exact fares, but it can't be more than €10. So, whenever you arrive in Ventimiglia, you can just catch the next train to Nice. Don't worry if it's not bookable in advance (it may not be); just book as far as Ventimiglia.