Well, looking at average ranges, 278w FTP would put me in the top 40% or so, which I would consider is reasonably average. Also, I'm reasonably heavy (around 100kg), so that probably makes it easier to put out some power whilst also meaning that I'm slow up the hills.
That's a) self-reported and b) among cyclists who track their power i.e. have power-meter equipped bicycle and a head unit to record stats. Self-reporting inflate the numbers by itself but, since most people don't actually have a power meter or/and don't bike, that group is made from quite fit people by selection.
https://www.cyclinganalytics.com/blog/2018/06/how-does-your-...