My chain broke so I brought the bike in and the guy told me "Well you don't have the old chain, so we have to replace the cassette also. They go together. If you don't replace the cassette then the chain will skip when you pedal hard."
Is there any possible truth to this, or is it just a scummy attempt to turn a $20 job into a $75 job?
For reference, the chain and cassette were both only about a month old, and had both been installed at the same shop - although they didn't seem to remember these facts when making the case for needing the new cassette.