I'd be unironically delighted if you could point me at some site helping me find what I've been missing like a goof, because it feels more like the question is "what isn't missing from the PoE sensor market?" It's pretty niche isn't it, with what little there is available also being at enormously increased prices? Take something as simple as "is there water where it shouldn't be", isn't there basically just the Aquo Proteus XE at $350 and, I think maybe one other I can't remember? Surely there are some "call us for a quote" industrial gear too but it's not exactly the common case vs z-wave/zigbee/wifi. Same with pretty much whatever else one might name. Like, what if you want a semi-permanent motion sensor (not a camera), are there any PoE options at all? I think I remember reading someone working on an mmWave one to get it work with HA but that's it. And yes 100% you can say that it's "overkill" or the like but looking at DigiKey's PoE controller pricing doesn't seem like it inherently has to be a huge premium, just isn't anything mass produced.
I mean, it is certainly very arguable that the entire IOT market is and always has been sort of a total mess more than not, and that PoE switches weren't the $50/8-port affairs you can get now either until pretty recently. I totally understand why it's not a thing, I want to be clear this is more of an idle wistful "that'd be a nicer world" along with all sorts of other areas of tech. And I know there are PoE splitters so sometimes you can get roughly the same effect if something has ethernet+power separately. Wireless is also certainly sometimes simply the most sensible option. Just would be nice to have more options when it counted is all. I've dealt with enough odd spaces where it's a pain to get any signal in and even if it's only once every few years it still sucks to have to have somebody work their way in there to replace a battery and sometimes things randomly fritz out, makes one long for good ol' hard wire with super easy ways to just power cycle the switch and eliminate lots of complicated stacks of networking. Ah well.