You didn't look very hard[1]. It's a research project funded by grants and donations, and as far as I can tell they give away their databases[2].
[1]: https://plantnet.org/ [2]: http://data.plantnet-project.org/datamanager/_design/dataman...
[1]: https://plantnet.org/ [2]: http://data.plantnet-project.org/datamanager/_design/dataman...
I was alluding to Apple in my comment, as they are the ones that have a model for their mobile devices being some sort of knowledge lens. They are very easily capable to eat the cost of maintaining the database without resorting to some sort of exploitative business model.