It still isn't affordable. You can get a phone add-on from FLIR for $180/$200.
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.
Kudos for this project though. It is important to have well documented open source hardware in a as many field applications as possible.
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.
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.