That is about what the machines in cabinets go for at our thrift store. I think that some people buy them just for the cabinet. I have a couple that I have picked up for $20 or less, but I have never gotten all the cams like you did! They must be easy to lose because they are never all there. I bet if you Google the cams to see if they are available, they will be worth a lot more than $18.
I managed to sneak the last machine/cabinet that I bought at a thrift store into the house without my husband knowing about it! Pretty impressive, huh? :0)