It is no secret that the vast majority of my domain names are .com domain names. I own and have owned some non .com domain names, but my focus is .com. That said, I have sold a handful of non .com domain names. I would estimate that the figure is probably about 3 but it could be a few more from a long time ago. One off the top of my head is a .net that matched a .com I sold and I also sold a package of 5 names in the same extension.
Have you sold a non .com domain name before? My guess is that somewhere north of 75% will say yes given the number of people who I know buy ccTLD domain names and there are also quite a few people who have had varying levels of success with the new extensions.