I've checked for that claim and it turned out that it's from Stephen Zaloga's book about French WWI tanks. I misremembered it it - it was field 5 Renaults for every 1 Schneider without price mentioned.
Saint Chamond's gun had much greater range than Schneider's, though.
According to the Chars Francais site one FCM 2C costed 2,000,000 Frcs in 1920 O_O .