You're an idiot if you think marginal cost has anything very much to do with the price charged to a consumer. Don't you think that, given that the custom is what the custom is, the hotels analyse their occupancy and set rates to make a profit depending on these factors? Frankly, who cares where the custom comes from? It reflects that status quo, and any change from that position will impact rates somehow.

In this case, you'd see one rate that was lower than the existing double-occupancy rate and higher than the single-occupancy rate. If most rooms were already double-occupied, you probably wouldn't save much at all.

Personally, I think tipping culture is well out of control in the US. Hotels and restaurants could pay their staff enough to make a reasonable living so they didn't have to depend on tips. I'm not stupid enough to think that would happen without an increase in prices though. Do you see the analogy here?

Of course, in most countries that would be illegal. It's also such a completely bogus false analogy that I won't even bother commenting on it.