Are people buying off the shelf sliders…..not the main ones like Revolution etc but the thumbnail scrollers and the Clients thumb scrollers that you see on most themes.
If so where do people buy them…I do not see them on codecanyon?
A lot of the things you describe are open source libraries that authors choose to include in their themes. For example http://caroufredsel.dev7studios.com/ is a commonly used carousel that is both MIT and GPL licensed.
There are also a lot of libraries for sale on CodeCanyon that do what you describe. Maybe you’re searching for the wrong terms? I can’t link items directly but if you do a simple search for “carousel” on CC you will find a lot of stuff.