For the use cases that I personally, still, use tablets for? About 100-200 bucks depending on how powerful the hardware is. Because otherwise a person CAN find ways to live with a sub 100 dollar 10" Fire tablet, or 180-ish 11" Fire max tablet. But the problem is, Microshaft wants that much just for the OS license, which as I said, completely kills any chance of a non-Microsoft tablet manufacturer being able to make enough profit off the margin to be worth doing, even assuming they get bulk licenses for half that. Now, if it was MS themselves making and selling the device, since they of course could include the OS at no cost to themselves, they might be able to do it but for what the majority of people do on them these days it just doesn't make much sense to spend money on an additional device to do things your phone can already do.
So, it basically MUST be a situation where you HAVE to run a Windows-only application otherwise it simply doesn't make sense and even when that's the case, as has been mentioned, there are other very light and far more capable devices that run Windows which just make more sense these days. Not to mention the fact that, like USAFRet said, a LOT of devices out there that can or must be remotely controlled will only work with iOS or Android apps, which further reduces the need for that type of Windows device.