We had split the map data sources to not drive customers away and we split our licensing between our app and the map subscription. It was an interesting problem, we had one employee that only did OpenStreetMap - keeping maps up to date, manually solving problems etc - this was actually much cheaper than buying TomTom, but still we couldn’t match the quality of TomTom. So, we would recommend: do you need high accuracy maps, buy TomTom, otherwise use the cheaper variant.
We were also implementing Here Maps (the old Nokia Maps), when I left, and it looked really promising, but I think the same licensing scheme, only “cheaper”, we could make do with only about 100k in pre-bought licenses