I use Titebond III also, I have no idea if Titebond II would be equally as affective or not. However, I think of III as added insurance and piece of mind. It's always my preference to want to over engineer the situation, maybe not necessary, but better than the alternative. :)
Considering the volume I need, and the reasons for my becoming a Beek, the cost difference really isn't an issue for me. I can appreciate that if someone was large scale and profit was their primary motive, the cost difference would be an issue certainly worth taking a very close look.