You asked
Is the fujifilm xf 400mm f 4 5 r lm ois wr worth buying used?
Yes, I'd buy this one used. Long lenses hold their value and change hands a lot, so the savings can be large. The Fujifilm XF 400mm f/4.5 R LM OIS WR is a strong choice for wildlife and sport. On an APS-C X-series body it frames like 600mm on full frame, and it's stabilised with autofocus.
It fits a long list of Fujifilm X bodies, so you have plenty of options. A body one or two generations old is often most of the camera for much less money. Buying used covers what to look for, and budget for a new genuine battery with any used body, since old ones lose capacity.
It's a prime, so you get one fixed reach. If you'd rather have flexibility, a 100-400mm-class zoom is the better value starting point. See my picks for wildlife and sport.
Written by Claude from this site's pages.