I doubt it's safe to say that the game is any more likely to drop an r9 15-22 damage sword than it is to drop an r8 15-21 damage sword. So the only rarity here has more to do with the odds that fewer players would keep a sword like this to try to pc/sell at all rather than simply merching it outright.
(There may also be fewer folks playing where foes are likely to drop r8 15-21 swords.)
There
are some players around who enjoy collecting non-max items. There aren't many of them, but they're well aware that the items they're collecting aren't max. I've chatted with a few of them, and I'm confident they like this stuff for reasons other than the implied,
"duhhhrrr it's q8 ... ooo shiny ... duhhhhrr" There's no wonderful new functionality they get from these items, but there's no wonderful new functionality boost to support most of the fair market value prices for weapons in this game either.
To imply the people collecting pixels you don't care about must be doing so for only stupid reasons is pretty self-centered and narrow-minded! I'd merch Crystalline Swords rather than keep them, as I find them beyond absurd looking. But there are plenty of other players around who quite enjoy them! Just because you don't like certain pixels or stats does not prohibit the rest of the playerbase from liking them. PC thread replies are supposed to be your best, educated guess on fair market value, not what something is worth to you.
If you do not care to keep this one yourself and want to sell it, I think you're perfectly "safe" selling it for whatever high offer seems worth your trouble. It's very unlikely anyone is going to make powertrading profit off you here, as the end market for these things is pretty small and niche-y already.
Krystal is fond of his Short Sword, and to him, it's worth more than 40k - that's his choice! I would not PC either his sword or the Brute Sword in OP as other than something like ...
Possibly merchfood and probably not likely to get very high bids, but some folks collect those. If you want to bother selling it, list it for bids in a Low End thread and see who's interested. Set a reserve at whatever limit strikes you not worth the trouble selling anything at all.
Cheers & GL!