Traveling to Barcelona by cruise boat and want to take a bullet train from Barca to Paris on May 11, 2024. Which source sells cheapest second class tickets, when should I start looking to book it?
90 to 120 days in advance at this site:
https://www.sncf-connect.com/app/en-en/home/search
You can put your email address and the site will alert you when the tickets go on sale.
The company that actually runs the trains, in this case www.sncf-connect.com
SNCF Connect is the cheapest way to book. Sales should open about 4 months before, sometimes a bit earlier even: SNCF Connect lets you set alerts.
I find that First class is worth it on such a long ride (6.5 hours), and not much more expensive if booked early.
By the way, Barça is not a usual nickname/abbreviation for Barcelona ;)