What does $2000 more get me with the RX1 that I don't get with the EPL5?

I had a "full frame" camera with 40 mm fixed lens 40 years ago, the Trip 35. If you want to try the format, get one used (they are very cheap) and shoot a few rolls of film. It's optically a pretty good camera. If you don't feel limited by the single, fixed lens of the Trip 35, you should be fine with the RX1 (which is of course even better in most respects except the missing viewfinder).