Unless you can make a library that is considerably better than what is open-sourced you will be out of luck. But, on the ASP side there are some for-pay component libraries that make it easier for developers, so it can work, depending on the market focus.
jQuery won't be anything other than free, I expect, as John Resig, the main person behind it, seems to be very involved with open-source, since he is heavily involved with Firefox development.
There are many benefits in learning how to create your own library, depending on your interests. In the past it was almost a rite of passage for Unix programmers to write their own shells, I can see the same idea for people to write their own frameworks.