I’m sure as a percentage of extensions you’re probably right, but who installs extensions by browsing the entire catalog of extensions?
What I’d bet most people (including myself) do is search for extensions (assuming you don’t already know the exact one you want). My experience has almost always been that the extension I want isn’t available for safari (just chrome and Firefox), or is a shitty/old version of the chrome one.
So even if the $100 keeps some more junk out than on chrome, I still don’t get to use the extensions I want and the ones that are available aren’t great (albeit better than junk).