Q D b D,
For the most part I pay from $5.00 to $15.00 for cam sets here at my LSMG and on GW. They are not rare or uncommon at all.
The MW ones fit machines the Signature machines. But there are different versions of those just like there are different versions of Kenmore cam machines. And I don't know which models your cams fit.
The Singer cams are all over the place. I have many duplicate sets, got 'em all cheep too.
I know, I'm not much help this time am I?
Joe