I'm talking about ALL of Fallout New Vegas but in Dead Money alone there's 3 things I can't justify.

1- How do the hologram vendors accept caps? This was a pre-war casino and should have no knowledge of caps as a currency.
2- Ghost People. There couldn't have been more than 50 of those Hazmat Suits delivered to the SM. Dean Domino's dialogue suggests there's so many they fill the sewers and the buildings. This is just not possible.
3- The third is a bit of a question more than anything and it's kinda maybe answered by Dean Domino. He's been in this casino for over 200 years. They haven't run out of edible food yet!? Seriously? He says "I still need to eat, at least I think I do." so if he DOES need to eat, what is he eating for 200 years?

Feel free to add your own.

Theres a lot that does'nt add up about Dead Money. The main thing being, how the hell did they think it was playable and fit for release? Or that any of the combat or repetative, no fun, quests were a good idea.

I played it twice, it broke in the same place twice, said frag this and never bothered with it again.

But yes, I did wonder about Dean Domino and eating.
The Sierra Madre machines make food and clothes, etc like replicaters and take sierra madre chips. So long as you have chips, you have food,clothes, etc. And they take chips you make yourself.

The Ghost People. I did wonder about the suits, but maybe they have ways to make them. Or theres loads so they've enough to use on new ones.
Maybe they use the sierra madre machines to make them.

The hologram venders, I never stayed long enough to work out what the hell was going on there.
But, maybe caps are like chips, so they accept them. It is a bit puzzling.

What I don't get is this.

IN OWBs, Vera Keyes song is played constantly. The song you play to open the vault.
So how the hell, did Elijah not notice this? It's on the Sierra madre broadcast, FFS! The exact same song!
He was listening and testing, and SAMPLING the sierra madre broadcast, to test collars on chinese ghouls.
He could hear the radios blaring the exact same song all over the Big MT. The sierra madre is mentioned in all sorts of places. Holograms. Terminal entries.
And he did'nt think Vera Keyes, sierra madre, Vera on the radio constantly, clearly. Maybe I should should sample that song, in case it's important. Vera, SInclaire, they're mentioned as being connected.
He did'nt record it?! Make a connection?! Would have saved him and every other poor person that encountered him the trouble if he had.

Suspension of Beleif. Are you really going to conduct an investigation of how those ghost people got there while they're constantly tossing super-sharp spears at you? As for the rest...

1. No clue. The again, the caps you get are part of the Seirre Madre area. It's possible that the Vendors were programmed to accept Sierre Madre caps as a trade item back when it was a hotel. Otherwise, the "selling stuff back" to them wouldn't be at all believeable. It's possible that the courier asks for their change as caps, not pre-war money.

2. There's no word on how many suits were delivered by Big Mt. However, we do hear how the workers having to cut themselves out of their suits after they've been in operation after a short period of time. It's likely they kept getting new suits sent in from Big Mt., but weren't able to send back the damaged suits, or move them out of the Sierre Madre as trash. The Ghost People find these suits, patch them up, and all that. Besides, most of the people at the Sierre Madre may have become Ghost People, not just the maintence guys. After all, they LOOK like they can resist radiation and whatnot...

3. Ghouls have lower-than-average metabolism. After a few years, the Shroud completely enveloped the Sierre Madre, blocking daylight. Lacking cues for mealtimes, Dean probably got into the habit of doing things based on his internal biological rythims. Since he has a slowed metabolism, that means his biological rythims are also significantly slowed. Assuming the Ghost People don't eat, that's a lot of food for one person to eat, say, maybe once a day or once every few days.

As for the above's question... Elijah probably suffered from tunnel vision. It's known to occur, and serious mistakes have occured because of it. Other, more viable options aren't considered because the person is so obsessed over one detail. Besides, even knowing what opened the vault would do him no good, he needed a series of events to happen in short order to actually open the hotel to even get to the vault. Also, there's no real indication that Sinclaire had keyed the lock to one of Vera's songs in terms of hard evidence that he had access to at the time, aside from Dean's hunch. And Dean didn't seem like he was willing to share with Elijah, nor does it seem that Elijah was willing to ask Dean for what he knew. "That ghoul's been collared by Dog. Dog collars people from outside. Thus, that Ghoul wouldn't have any idea about this place."