Worth $400?

Went to the thrift store this afternoon to just walk around and try to get Henk tired enough to sleep for more than 30 minutes.  The Yellow Brick Road store has done a complete over haul of the store layout. One new feature is a wall of very $$$$ books. I've been looking for a first edition of Julia Child's books and was super excited when I saw this but more shocked at the price tag of $400!  It is signed but it's the fourth printing which I wouldn't think was as valuable .  When I got home I ask my book guy if it was worth $400 but he needs the bar code information, so we'll be going back to tomorrow to get it. I know with all the new apps out to find out what things are selling for, thrift stores are starting to raise their prices. Pickers are having a much harder time finding things they can flip. 

Update: This book unsigned is worth $48, so the question is does the autograph add $350.00 to it's value?