As others pointed out herbs might be the only thing that come close to being cheaper. Speaking oft herbs - Weed might be the only thing that fits your requirements thats actually cheaper this way.

Omg that song is awesome. Thank you for the recommendation!

As you are asking this in a privacy community I would say Graphen. But as you want to keep gmaps you might also want the comfort you get with e/os when also using their cloud. Personally I would recomend a used pixel 8 with e/os and to try mapy.cz to replace gmaps. About going back to stock OS if you choose a pixel flashing images is stupid easy :) so no worrys there.