matthieutje65 (12/09/2012)
Aluminium is quit expensive if you want to make a mould you need quit a big massive block of Aluminium

Yeah but his mill is only small, so I don't think he's going to be machining massive slabs of anything 
Ally compared to good quality PU or epoxy model board isn't actually too expensive, especially when you take into account the time it would take to get a compareable surface finish by sealing lesser quality materials. Also if you have a part that is dimensionally critical you don't really want to start adding resin / sealer to it in uncontrollable quantities.