end in itself
A purpose or goal desired for its own sake (rather than to attain something else). For example, For me, writing books is an end in itself; they don't really make that much money. This expression employs the noun end in the sense of “final cause or purpose,” a usage dating from the early 1500s.
Examples from the Web for end in itself
We have a moral aim only as our purpose coincides with some end-in-itself.Human Nature and Conduct