I'm a Nevadan (Las Vegan is a terrible unused term, we haven't collectively agreed on a replacement) and I'll tell you, even for an important mega company like the UFC, buying land in this city is a long and arduous process, especially considering zonings.
Apex is in a commercial area which already had shit built up around it.
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TKO bought that southern strip you see along Rafael Rivera, from Torrey Pines to the border of Golden Entertainment as far as I'm aware. Those N and NW plots of land are public-private investment partnerships with the city and various, perhaps dozens, of developers. They don't have as much room to work with there as you would think, but that's only as long as they keep being cheap and refuse to buy out the guys who own YH L&S and those other offices north of the Performance institute.
Fun fact, that Sierra Gold right next to the Apex is where I would go to watch every PPV as Dana gave them a lifetime free pass to show them (he would come in from time to time) but recently TKO revoked that and the bar is a ghost town from what I've heard as I haven't had a reason to go back myself.
I would actually like if the Apex was affordable to go to, as I'd have something new to do every other Saturday or so, but the tickets are on average more expensive than PPV tickets at the Arena, so it's been absolutely non-sensical unless you're the type that has more disposable income than you know how to spend.