I've been hearing the shortage thing since I started brewing in August of 2012. In fact, I was told that the very day I started and bought 2 ball locks at my LHBS. Now I'll give them credit, they don't normally have a lot on hand and a lot of times are out of stock, but if I needed a keg, I wouldn't have a problem getting one in my area. There is a guy on craigslist selling them all the time for $50 for local pick up.
There is definitely a supply and demand issue though. At one time, there were more on the market than people who needed them. It seems to have kind of balanced now and the days of give-aways to get them out of the warehouse are obviously gone.
At $80 though, I'd definitely just go ahead and buy new. If you really shop around on the internet, there are places that you can get a new one (Italian made) for about $100.