ois?

been shopping around for a motor. i got a 92 johnson with ois ignition that was submerged and is siezed. was thinking of rebuild but, thought i would look around first.now i am confused. every time i see a 92 ois johnson they want top dollar. wbr has a 90 johnson 200 for $1000, a 96 175 evinrude for $1000, and a 92 175 johnson ois for $2250. all are described as good running engines with good compression. everywhere i look that has a 175 ois wants more than comparable motors. can someone tell me why. hopefully skools will jump in here.