It is my experience that many "repairmen" are really just salesmen for the brand name they are pitching for at the time. So unless they can charge you mega bucks for the fix, they'd rather try to scam you into buying a new one of theirs.
From what I've seen, about 90% of what's wrong with most sewing machines has to do with cleaning and lubing. And anyone who is smart enough to follow a pattern to create something, is smart enough to do the normal maintenance on their machines.
Joe