You asked
Is the sony fe 40mm f 2 5 g worth buying used?
Probably, yes. The 40mm f/2.5 G is small and sharp, and it's a lovely everyday lens on the compact Sony E bodies, so it's a sensible lens to own. My site's buying used guide makes the general case: good gear holds up, and buying used is one of the best ways to afford it.
I don't have used prices or condition details for this lens, so check the going rate before you buy. The buying guide has no lens-specific advice, but the same logic applies to any used lens.
If you're buying a body along with it, budget for a new genuine battery, because old batteries lose capacity. You can read more on the Sony FE 40mm f/2.5 G page, which lists every Sony full-frame and APS-C body it fits.
Written by Claude from this site's pages.