For your frontend: MapLibre GL  is the fork of Mapbox GL that's still open source, so you don't have to pay for each usage.
For tile hosting: Openmaptiles , based on Openstreetmap data. Either pay them for out-of-the-box experience, or use their open-source code to set up your own server at whatever hosting for whatever price you prefer.
Plus one for this. I created a wrapper in the language I use for HERE maps, and their fremium model is great. Over 250K I start paying, but I haven't got there yet. I'm using routing, address auto-complete (International), tiles, traffic maps and so on.