Quoted from Frax:

User error, or other aberration such as being in an Xpin booth?
My games go to Texas Pinball Festival, which should be obvious by my location? Unless his game was at CAX or Pinburgh, not sure I'd take that without a grain of salt. My audits from TPF largely mirror what other people have echoed about their games, which is generally in the range of 400-650 plays depending on the era of game and how tricked out it is.
Medusa is a rarer game that people would seek out, so I might expect slightly higher numbers, but not on the order of 20%+