I think the time of expensive apps is pretty much over.

GPS Navigation being the last stronghold (70-90 Euros). But even here we see changes. Google Navigation is already free and caused a drop in the GPS makes stock prices. It would be easy for Nokia to provide free turn-by-turn navigation since they own Navteq!

One thing the Apple app store showed, cheap software can still make you rich. Yes I know, it does not really work for the Android market right now, but I believe that to be a technical and an marketing issue with the marketplace app.

One last thought: Why do you think there won't be pirated software for the N900? Look at the N810 and the navigation add-on for Maps.