From what I have seen in my area a used saddle of good quality will bring several hundred dollars. But it has to be in very good condition...no rolled leather, not beat up, and a known brand.
As long as your saddle is solid (I wouldn't guess the weight of it from the photo), it fits you and your horse, and you can replace the sheepskin yourself, I'd use it and enjoy it. It's hard to say what it cost new 50 years ago, so much has changed. Seems like comparing that time to today is like apples and oranges. It's hard to find a good all leather saddle today for under $1200 new...and that may be a bit conservative.
By the way, I love the "ears" in the second photo.
If you ever find yourself in a fair fight, it's because your tactics suck. ~ Marine 1SGT J. Reifinger