You caught me off guard on this thread. I thought this was a forum thread for rehashing the same old York topics; admission to high, public not allowed, open too early/open too late, merchandise priced to high, why do vendors bring the same stuff, is York worth going to, why don't they bring York to my hometown, etc.
I have never gone to a train show, flea market, or garage sale with a preconceived plan of what to purchase. I just go with an open mind and open wallet. Heck, the last train show I went to I bought 52 brand new Makita SDS-Plus carbide tipped drill bits for $20. Never seen them at a train show in my life.
But, now that I have a smart phone, it is so easy to check ebay completed sales on what items MIGHT be worth. I always end up buying things that might be handy or nice and make the final decision when I get home on keeping it or selling it.