What's your definition of affordable? I use ones similar to these: http://www.ebay.co.uk/itm/JSHIP-DIGITAL ... 1c26ae89ea

Mine were second hand though so were around half that price.

I know some people use the scales in the fruit and veg section of their local supermarket and some use the ones in the post office, as Ellis said. I used to use our digital bathroom scales which were only accurate to 100g, but since I never seem to build robots anywhere near the weight limit, that wasn't a problem

Nice use of the WiiFit board though. Likewise mine hasn't seen any use for close to two years!