We did have a thread about tuber production numbers a few years ago but I can't remember the data.
Perhaps the real Buell anoraks like CJ, Adam and
will be kind enought to do the honours.
In ball park figures, I think the world-wide total number of X1's would be of order 10,000 with perhaps about 10% of those having come to the UK. S1s and skinny M2s will be rarer still - I think the offical UK figure for 1997 Buells was only about 500 bikes, i.e. ~300 S1 and ~200 M2.
I also recall a few months ago
more or less advised someone to scrap a high mileage M2 as it would have been beyond economic repair, so these bikes will be becoming rarer with time - at least until we get good community 3rd party spares arrangements in place. When I was particularly active in MAG / FEMA about 10 years ago, 3rd party spares was one of the hot riders rights topics of the day. This was because major manufacturers were trying, under the aegis of copyright protection, to lobby the EU so that 3rd party spares provision would become illegal under EU law. Thankfully they lost - so riders are not tied to only getting spares made by the original manufacturers of their machines.