Xcceries via eBay offers this 16" Unicycle with Stand
in six colors for $39.90
with free shipping
. That's tied with our February mention, $3 under the lowest total price we could find for a unicycle of this size elsewhere (outside the mention below), and the least expensive unicycle we've seen. It features saddle guards and a a skid-proof 1.75" tire. It's recommended for riders under 110 pounds and between 45" and 61" tall.
A close price: Frugah offers one in Green for $41 with free shipping.