the BUSes in this departement only cost 1,50/ride, 1 change included.
There is also a carte ZOU=daypass for all TER-trains in the whole of the dep., cost is 15/day, no morning time limit, thus a little cheaper as 2 singles long way.
(BTW: today, this weekend there is a very special low promotional fare of just 5 for the WHOLE of PACA, as in FR there is ''open day for historic monuments'', this would alow you to go Ventimille-via Marseille to Avignon, or even on to Briancon, on TER-trains).