Sorry they are so expensive but they are genuine vintage Jones bobbins, not Singer and not modern repros. They are very rare and hard to find. These Jones Bobbins have a unique design. They have the normal ‘Singer’ type disc at one end with a small axle point. 

At the other end they have a Dome with a tiny hole that ‘locks’ the Jones bobbin in the jones bobbin winder. A modern bobbin or singer bobbin does not have this locking ability. The ‘lock’ ensures the correct tension when winding your bobbins.