First, you need to find out if the kites are made by "Go Fly A Kite" or by Joel Scholz.
If they are by Joel Scholz they will be "Sky Delight" kites and NOT the Joel Scholz Signature Series which was licensed to GFAK.
Assuming the kites are the Sky Delight version and in good condition, they might be in the $125 to $150 range. That is just my opinion. A few years ago, they would have gone for more, but the recession has really dampened kite values.
Hopefully, others will chime in.