The person you are replying to is asking about operating costs, not manufacturing costs.
There's no way they are regrinding and resurfacing the mirror periodically - cleaning, sure. But redoing the surface? I'd like to see more info please.
The perfectly shaped glass is the expensive part - coating it is not the expensive part. So despite drinking, I did not get my answer on how this telescope costs $100million a year to operate.
Additionally it does not costs millions to operate this resurfacing machine. Building it? Sure, I could see that. But running it? No way.