Like most questions here, the correct answer is: IT DEPENDS!

Back in the good old days of 6 speed drivetrains, a chain would last 10K miles or longer, even if it was neglected.

The narrower the chain, the faster it will wear. I assume we shall be discussing only 10 speed chains.

I have heard anywhere from 2K to 6K miles. Depends on how often you clean/lube it, how gritty it gets, how hard you ride it, etc.

Most folks get 3-4 cassettes from each chain. YMMV.

Chainrings should last pretty much forever (at least 50K miles), unless seriously abused.

Best solution is to measure your own chain as suggested above rather than go by number of miles.