Seat reservations on Eurail are often expensive because they are not controlled by Eurail itself, but by the individual national railway companies (like SNCF in France, Renfe in Spain, or Trenitalia in Italy). These companies view high-speed and international trains (like the TGV, AVE, or Eurostar) as premium services with limited capacity. By charging a reservation fee—which can range from €10 to over €30 per segment—they manage demand and guarantee that pass-holders do not "crowd out" full-fare paying passengers. Furthermore, in 2026, many European railways have moved to "dynamic pricing" for reservations, meaning the cost can increase as the train fills up. While your Eurail Pass covers the "base fare," the reservation fee covers the cost of the specific seat, onboard amenities, and the speed of the service. To avoid these costs, savvy travelers often use the "No Reservation Required" filter on the Rail Planner app, which routes you through slower, regional trains that are often just as scenic but may take twice as long to reach your destination.