You may think these are ludicrous prices, but think of it as market segmentation. It seems like they're only a few employees, so if they get, like, 300 companies in the entire world to sign up for email support, they earn a pretty respectable salary. Or if they get, like, four companies in the whole world to join their consortium, and nobody else buys anything. In fact, there are four consortium members on the homepage: https://sqlite.org/index.html and possibly others who chose not to be listed. So we have (it seems) two people getting paid $600k per year to work on this. This is a software SMB - they're not trying to hyperscale or squeeze every penny, just make a living selling a good product at a steady rate.

This model only works, of course, because SQLite is a genuinely good product that everyone loves and uses for free in every open-source project. It wouldn't work if a copy of SQLite cost even $10, because then we'd all be using MariaDB. It might not even work if it was proprietary but free.