Fifty bucks. Just kidding. Your fine rifle is worth around $500. That is just an approximation, there may be more value to it being in .357 as opposed to the more common 44 magnum.
It's a great rifle. They sell new for around 650-700 ish. I have the 44mag version of that rifle and I love it! Put some Skinner sights on that puppy and you have the bomb!