One great thing about buying used SAK's is the lifetime warranty. My son was at a Boy Scout Mountain Man Rendezvous many years ago, and won first place in a blackpowder blanket shoot. Accordingly, he got first choice of the items on the blanket. He was drawn to a nice hairpipe choker, but I encouraged him to get the SAK. He pointed out that the blade was broken, I said I knew that, get it anyway. He did, and when we got home we mailed it off and in a few days a brand new knife came to him. What a deal!
He learned that day to trust his old man a little more often.
Even if you get multiples in a "grab bag" buy, you can sell them at yard sales and make a profit. Especially after returning the broken ones for repair or replacement.
Love those SAK's.