I had an interest in these a couple of years ago because the technology was interesting. They were just too expensive for a lark*. They're still, I think, too expensive just for normal backpacking, etc. If you're looking for electricity, little power cells are around twenty bucks. or even good solar panels are still cheaper these days.
Currently the only use I could see for one of these for myself would be as part of a SHTF car kit or something, but they're still a bit expensive for something you would stick in an emergency kit. I might buy one around $40 or so.
*At the time, I recall finding a few Youtube videos on how to build one for less than half the price with mailorder Chinese thermoelectric converters.