I've had that conversation regarding certain machines. Each time the issue was some older plastic gear (not necessarily the same gear each time) had broken a tooth and the repair person was not hopeful of finding a replacement gear that would be in good condition. I think this is a primary reason so many people love the even older machines that are all metal and thus less likely to have this sort of issue.
If the repair person gives you the "not worth fixing" speech, find out why they are telling you that. Then you have a solid basis for deciding if you agree with them or not. Good luck!