Well, I guess the cell's size would make for a nice variable to change between price points (cheaper ones having bigger cells).

Individually, each cell has the same precision as your N900 screen... which means that as long as not any two fingers fall on the same cell, the screen will be very, very precise. When two fingers fall on a single cell, that cell will report the average point much like the N900 does.
I do not think that would be a big problem since:
a) With small cell sizes, you would need to have very small fingers to be able to trigger this,
b) You might be able to do more accurate fake multitouch on such a smaller cell.