5
strips are better but its still a tiny thin part for making in a chemical pressure mold
also with heaters something that raises cost alot is temperature. The cost sky rockets over ~1400C (as soon as you go more then nichrome and kanthal give)
then you start having ceramic heating elements. and then you need to control offgassing from heaters too, and it actually needs power electronics. its not in the same league as cheap stuff like porcelain (still expensive for quality). Geometrically stable chemically inert mold at 1500C. I wonder how long those last.
I think alumina you can press then heat. which makes it much cheaper, since you are not baking it under pressure
also, AlN comes in a bunch of different grades. the ones with the best thermal conductivity probobly are the worst processes. IIRC the performance of the cheap one is very poor for thermal conductivity, if you are after those 'nice' numbers