Lpc2000

> But such an approach <4 layer> highly decreasing the advantage
> of the low cost of the LPC2000 series.

Almost any board can be laid out with just 2 layers if you have
enough 
room.  But keep in my mind that is it possible to make a 4 layer
board 
a lot smaller than the same board as a 2 layer, since you don't have
to 
leave room for power traces.  Also, it usually takes less time to lay 
out a 4 layer board which may affect economies on small runs.  

Keep down the cost of 4 layer boards by "panelizing" them.  Place a 
matrix of small boards on the most economical large board size your 
supplier offers, then cut them apart with a band saw.  Most layout 
software packages have a panelizing feature or macro.  Place long XY 
traces on the panelized board to guide the cuts, then smooth the cut 
edges with sandpaper.

Bill T.
http://www.kupercontrols.com