I've had a Jet 1642 for 10-15 years now and my on-off switch did go bad. I checked through Jet and the 'assembly' was something like $70-$100 when I looked for it several years back. From what I remember it was for more than just the switch, it had the button and some other stuff with it IIRC, I checked on Ebay and found the switch for something like $10, so I bought 2, one for immediate use and one to go on the parts shelf. Working fine but I always have another if ever needed.
I thought about trying to clean the old one, but those usually don't hold for me so I got a replacement.
My 2 cents.