You are getting the box as a lease but you are really paying for the Developer program.
Here is the page with the details.
Learn about the cutting-edge new features of macOS that you can use to build powerful apps and compelling games.
developer.apple.com
I thought about it as well but it really is developer-oriented. Going to come with the first ARM beta of Big Sur and almost nothing will work on it, like Word or anything else you might use, and it will probably finally be useful and have apps available about the time you have to return it.