The target demographic for OsmAnd is people who prefer to pay for services with money instead of their privacy. Google Maps is only free if you consider your personal information and privacy to be valueless.

Only on Play store, seems like a good "market segmentation" spot to me.

If you can live with your maps only being updated once a month, it's a one-time payment of 25€ for the entire world. I don't think that's too expensive? You can save some euros by waiting for a sale (there's one right now in fact), or by buying just the Europe maps for example, but... I really didn't think it's too much.

On the other hand I can agree that the subscription feels more pricey, but if people make use of the hourly map updates it's probably quite justified, given the bandwidth costs.

I paid a small once off amount and it's for life.