To be fair, OsmAnd bears the cost of hosting those maps, and when you consider that OsmAnd+ allows you to literally download the entire globe for offline use (which translates to hundreds of gigabytes of traffic), it's clear that they need some kind of ongoing revenue stream to be sustainable. And hillshade tiles (3D terrain) are particularly large since they need to be bitmaps rather than vectors like basic maps, so making their users bear more of that cost is not unreasonable.