I was listening to the radio when I caught a bit of the following piece. This guy (John Choate - former Navy SEAL and a security consultant) spent a year working for Wynn's on casino/hotel security. He does bring up Disney using metal detectors as a way to actually boost profits even with the additional costs. His rationale is that it makes customers more comfortable that they're at least addressing security concerns.
http://www.npr.org/2017/10/02/555170215/how-casinos-secure-against-active-shooters-and-other-threats
SIEGEL: But do you mean - do I have you right, though, saying that at at least either the Wynn or the Encore, the places that you consulted with, that if a man were to bring 10 weapons into the hotel to his room, those would all pass through a metal detector at some point?
CHOATE: I'm really not at liberty to discuss this particular (laughter) issue. But I can tell you at least for the properties that I've consulted at, that their ability to be able to detect anomalies such as somebody bringing 10 firearms into a location is quite robust.
I do remember in my stays in Vegas, possibly the highest security was at Circus Circus. It wasn't foolproof, but before going to the elevators everyone had to at least flash a room key. And with security stationed there always, they'd probably be looking for anything suspicious. Still - two large pieces of rolling luggage among thousands of guests probably isn't going to be terribly suspicious.