For the people saying "this isn't affordable," decent thermal cameras range in the thousands of dollars.
This is a great exercise in building stuff for yourself but not affordable at all.
The thousand of dollars cameras you refer to have very high resolutions which are really not the use case for the curious maker that would be interested in such a project.
But I agree that the price might be too steep for the curious maker who does not have a serious use-case that satisfies the investment on the long run
This is still a great project for a lot of educational use cases e.g. thinking of universities and high schools who want to envolve students in the build process.