Right. But you assume that the cost to make a transaction would always be 1 Nxt. Unless this is an ultimatum that cannot ever change, then I am not sure why this matters.
At the moment it does - and soon it will likely change to being 0.1 (from memory that was what was most popular) - so as I said some smart math guy could probably come up with some sort of formula that involves the "available supply" of Nxt and the number of transactions and predict the likely value of it (not me though as I am not so good with math).
Micro transactions are really not something that any blockchain is going to handle perfectly although with Nxt the idea of being able to regularly *shrink* the blockchain will certainly make it a better option than say Bitcoin.