IMHO, it is not the individual properties that have caused the volume of LV visitors to increase, it is the travel sites.
They purchase or guarantee large blocks of rooms at various properties, and put together packages with inexpensive air, etc that are true bargains. Many of "us" who love Vegas are not comped for the full monty. I could get a couple nights, but not the 10 or so I'd want to make my Vegas trips profitable.
I've booked direct with the hotels, and also purchased packages. Last one was a "Gay Pride" airfare & hotel for 7 nights, (coupon needed) and was less expensive by $100 or more than any other deal I could come up with. So I bought some pink panties in size XXXL, and booked it (3 times!) I think it cost me less than >$60 for 7 nights downtown, incl. RT non stop from S. Fla, hotel, and airport shuttle.
I would NOT have made those trips if I had not come across what I considered an amazingly low price I could not come close to replicating on "Orbitz".
The properties can keep on playing their "creative accounting" games. They can consider to screw the travel sites out of commissions. And, I suspect, the volume of Vegas visitors will decrease, or fail to expand, in part, due to that.
JMHO, of course.