I said it was a possibility and on lower end group sets it is pretty normal. I would say running 2 chains on the cassette could have eked out a little more milage maybe but 3k can be a lot and 3k with minimal maintenance could be a lot more. I don't mess around with chains and cassettes because I know customers will complain when it doesn't shift right and you tried to save them a little money and now they are having to pay extra for more parts that you didn't notice on first check in and you want to charge them labor and it gets messy. Solve the problem right away replace both have good shifting and you aren't spending a ton of money.