I agree that pricing really took off around 2012. There had been a very slow and steady climb up until then, but most pins (aside from some uber premium titles like MM, MB, CC or BBB) could still be had for around $3k or less all day long. Then it seemed like prices doubled on popular games almost overnight. There was a huge influx of new blood in the hobby and the long lists of WPC games for sale dried up completely. In the few years, it seems like even the C and D titles have doubled or tripled.