The 2FF is worth about 50¢ because it is popular with American collectors, these were printed by Beacon and Co printers in Boston USA, and came in with the American army in 1944 during the invasion of Normandy. It is popular with French collectors because of the tricolour flag of France on the reverse.
The 10FF note, only a 25¢ because it is a common note, very heavily circulated, most would not even collect it like that.