réservation price TGV 9713 Paris BCN.. octobre 9/ can first and second class cost thesame ( 27€). ??

Yes in France 1st class and 2nd class have the same seat reservation prices :

- 10€ limited fare, then 20€

Although the 10€ fare sells faster in 2nd class.

For international journeys :

- 35€ Paris - Barcelona (1st/2nd)

- 25€ south of France - Barcelona (1st/2nd)