steel today is bringing around 8 to 10 cents a pound when you sell it to the scrapyard, and you pay about .30 a pound if you are buying. When the price of steel went up, lots of good equipment went to the scrapyard as the economy was/is bad and lots of people sell running cars and useable equipment for scrap. Last time I was there, I saw a good looking 5' disk sitting to the side, they said an employee was taking it home but it was gotten out of a load of scrap.
There is a steel mill and scrap yard about 4 miles from me. I see lots of good looking cars and trucks and lots of farm equipment loaded and headed to the shreader. It's a shame some of the stuff they are selling. Us guys that like that old iron get our feelings hurt to see some of it going.
If the gearbox is there and turns and the blades are intact, go for it. May be nothing wrong but the front part of the shaft fell out. Look around, you may find that as well.