No, I meant Band Saw. Or Scroll Saw for that matter.
In that case, the only thing the RingMaster does is cut the rings faster and you don't have to glue the pieces together. No, it really isn't worth $600 just to do that. No matter how you cut it, they're all still in the "boards from a bowl" family.
As for cutting the rings on the lathe with a parting tool, many people do that. The only thing the RingMaster does different is cut from both sides of the board so you don't get tearout on the rings. Again, not worth $600 just for that.
To be fair, the RingMaster without the motor to attach to your lathe is only $400.
All seriousness aside, the only reason I have one is that I picked it up used for $25. If I had to pay full cost for a new one I would use the parting tool method instead. The only "difficult" part is getting the angle right so that the rings stack properly, with the inside diameter of the larger (top) ring matching the outside diameter of the smaller (lower) ring.