I got my THINNER (brand) scale for about $20 from bed bath and beyond. It was about .8lbs off of what the WW scale says when I go into meetings. It worked for three years so far, had a nice big digital display...
If you're unsure how accurate your scale is, and if it reads small weights (some digi ones won't read under 10 or something), find something you know the weight of and see what happens. Hand weights, bags of rice, that sort of thing.