guyanese (spelling?) redtails

[Them and Us]

i was thinking of purchasing a pair of sub-adults frome someone. he says $500 for the pair. i want to know is this a good price for the both of them? too high? too low? and they are about 4 - 4.5 feet in length. how old would that make them. they did seem quite healthy. very strong. not thin. did the "pinch" test and seemed great.