I have several of the toy sewing machines. Singer originally gave them to little girls in the 1950s-1960s when their Mom's bought a sewing machine. Great advertising gimmick; get the kids hooked on sewing!
The black ones like your two beige ones pictured, usually sell for a little more than the beige ones do. They are more valuable if the matching C-clamp and box are included in the purchase. They have been increasing in prices on ebay over the past three years. Usually the black ones go for anywhere from $50 up to $100; depending on condition and completeness of the collection. There is also an older black Singer. I've kind of been collecting toy sewing machines; have about 10 of them.