There's a very similar product (Freesync instead of G Sync) that's currently on sale @ $499 new. Not sure how that factors into used pricing on a Gsync monitor, but I believe the great majority of Freesync monitors are now Gsync compatible so it wouldn't be a big deciding factor for me if I were looking for a monitor.
I don't think all Freesync monitors will work because Nvidia certifies which Freesync monitor works. While you could manually enable G-Sync with a Freesync monitor, it doesn't promise it will work without glitching. The XB271 is not on the list but some of the XB273 are. So I guess you can't price it as high as a certified G-Sync compatible Freesync monitor of similar performance.
XB271HU is "real" G-Sync since it has the hardware implementation. It technically should command a premium to "G-Sync compatible" Freesync monitors, but in practice only G-Sync purists will care about the minute difference it makes.
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