I've often seen hotel rates that charge more for 2 people than 1. I know of Hamptons that do this for sure. But if you book the Hamptons on the Hilton website, if you enter 1 or 2 people, the displayed rates reflect the actual rates.

For more than 2, I expect to be paying extra, above what's initially displayed. I don't know really if there's a difference between that and what Expedia is doing. But as an experienced traveller, I'm used to it, so I accept that more readily than what Expedia is doing.

I'm not sure it's criminal, as Sheryl suggests, but it ain't right.