Hi,
I just thought I'd mention a useful resource I've come across. If you need chipboard (the thick cardboard variety) for prototyping, you can often get free scraps from any place which does framing for art (they just throw them away otherwise). I've done this successfully in both the UK and South Africa, and got chipboard scraps suitable for making folding boards, tiles and tokens.
Chipboard isn't all that expensive anyway, but why pay for what you can get for free?