I've done something similar in the past, but skipping the 'wooden template' step by simply using a projector to project sections onto the material (calibrated by use of a ruler matched to the projected image), then tracing with a texta.
Initially doing the cutting with an electric jigsaw, but that created a *lot* of nuisance dust - you ain't seen nuisance dust 'till you've seen polystyrene nuisance dust, the stuff electro-sticks to *everything*
. Turns out a snap-off blade utility knife with the blade fully extended, and held at a fairly low angle to 'drag' through the polystyrene, works much better and produces a nice clean cut (and doesn't produce the nasty gasses that a hotwire does).
For what I was doing I didn't need the precision you get from u.steinlechner's more traditional method, but I reckon you could get the best of both worlds (precision and even less cost) by printing the profiles on large format paper at an office supply store, and using a utility knife for the cuts.
I must say though, the hot wire produces some very nice circular holes
