How much is a complete set of Childcraft Encyclopedias copyright 1960 worth?

There is a complete set of 1964 Childcraft encyclopedias on eBay rt now asking for $75 and there have been no bids for six days, but there might be and the price could go higher, it's going to be determined by how badly someone wants them...if I were wanting to sell them, I would contact rare our antique book sellers and/or collectors.