I know of 2 Supermonos, both in Scotland. One is an Alastair Wager with virtually zero miles. The other is a factory original which the owner sold a couple of years ago for an undisclosed sum, believed to be around the £100K. This is the Wager one:
Now Suzuki have come up with a 'Supermono' engine https://www.morebikes.co.uk/58169/heres-the-official-designs-for-suzukis-supermono-single-cylinder/ https://www.cycleworld.com/suzukis-supermono-engine-design
Neither the Ducati nor the Suzuki solve probably the most significant power problem for singles which is pumping losses. having to get rid of all the air underneath the piston on the power stroke and dragging in fresh air when the piston is on the compression stroke, multiple cylinder engines can transfer the air to underneath those pistons which are ascending or descending as required
