I think the base room cost is negated as they iirc are decided on overhead and %occupancy.
The hotel has far more greater costs to enable them to accommodate and isolate members of the public. As I pointed out this morning, the boss has said that insurance is a huge uplift on him.
They also have to provide (on top of normal facilities), 3 meals per day, 24/7 security in sufficient numbers wrt numbers of guests. I don't know for sure, but would suspect staff will be looking for bonuses or enhanced rates due to the risks. Cleaning will have to be more regular and thorough too, so all in all, it is not difficult to see why costs are high.