Marketing strategies are very subjective and the decision process and priorities vary by company. Of course the same is true for buyers. In the end the buyer rules.

How long will these devices be able to be used on battery and what kind of battery is used?

I had a Stowaway or something like that, it was foldable, and you could even put your device on it to have it static in a good view modus (not necessary with N810). It costed 25 USD on eBay. So I find a price of 3x as much... high.

Also, I guess the support on the NIT for this Nokia keyboard is 1) because its a Nokia product 2) guarantees perfect integration. This is important for some customers.

SU-8W uses two AAA batteries and claims 50 hours battery life.