What do night buses from Paris cost and which tickets are valid for them? This question is prompted by the unexpected result that the RATP app shows that a trip e.g. from Porte de Charenton at 00:40 to Massy Palaiseau taking both the T3a and the night bus costs 2.10€.
This seems to suggest two unexpected things. 1.) The same ticket for the T3a can be reused for the night bus (the same doesn't seem to be true for the RER which requires a separate ticket). 2.) The night bus from Paris to Palaiseau costs 2.10€ while this goes through 4 zones which for a normal (RER) ticket would cost 4.10€.
Is this correct? (I am used to night buses being more expensive, not cheaper, which makes me skeptical.)