SNCF isn't one train company. Prem's, Ouigo, inOui, Intercités and TER all have different pricing logic, advance windows and refund rules. Pick the wrong one and you pay 3× more for the same seat.
A train ticket on the same Paris-Lyon route can be €19 on a Tuesday at 11:47 and €120 on Friday at 18:00. The "best fare" isn't a number — it's a strategy: which operator, which booking window, which fare class.
The hardest part isn't the price — it's that SNCF Connect, Oui.sncf and Ouigo all live on different pricing rails. A seat sold by Ouigo (low-cost arm) cannot be exchanged onto a TGV inOui seat, even for the same train.
The single best combination of operator + fare tier for your inputs. If a cheaper alternative exists with a real trade-off (no exchange, fixed time), we say so.
SNCF opens TGV tickets 4 months (~120 days) before departure, with first-batch Prem's released at the cheap end. Ouigo sells up to ~6 months out. Earlier = cheaper for both, but Prem's allocations are limited.
Prem's = cheapest, non-exchangeable, non-refundable, only on inOui. Seconde/First = exchangeable + refundable with fee. Ouigo = low-cost, no lounge, paid bag, optional seat.
Yes for the same train. The catch: Ouigo trains stop at secondary stations (Marne-la-Vallée instead of Paris Est for the East, etc.), seat selection costs extra, and you pay for anything beyond a small cabin bag. For solo travelers with a backpack, Ouigo wins. For families with suitcases, inOui Prem's often ends up cheaper once you add bags.
If you take ≥3 round-trip TGVs a year, yes. The card gives -30% on Seconde and -40% on Première prices (off the flexible fare, not Prem's). Heavy travelers use it as the default and apply the discount on top of any low-fare inventory.
A different Ouigo product operating Paris-Bercy ↔ Dijon/Lyon/Nîmes/Marseille with longer stops and slower timings, but cheap. Useful for Burgundy wine country visitors who'd rather skip a car.