I’m not too familiar with the whole “pay gold to get run through raids,” other than seeing the services offered in-game.
I noticed one guild “Los Mercenarios” on Ragnaros realm and their GM “Kezia” having 689 Heroic Queen Ansurek kills.
I saw that number and was amazed. So you mean to tell me that people do this for a living or something?
Yes they do lol
Absolutely. If there’s people around wanting to cut corners there will forever be people offering to carry them through. This isn’t new at all.
It’s alarming because I am thinking they must be doing this for real world profit, not just in-game gold.
Maybe. Lots of guilds do this for their progression. Building up large stock piles of gold for BOEs early in raid pushes. But could just be people hoarding gold and maybe selling accounts.
I could see that to some degree. But over 500 kills? I don’t know what they charge for a run, but if you run 4 players through at say… 200k gold a piece… it doesn’t seem like anyone needs that much gold. 4 x. 200kG x 500 = ???
They gotta be doing it for cash at that point 
Yea, wouldn’t surprise me at all. Back in Cata I did some RBGs with Blood Legion. They had 100’s of banks filled with gold. They were having people join the guild to work on guild achievements. Was pretty weird, but they made absurd amounts of gold running people through content. Basically as soon as the world first content was done, it was doing carries and building gold for the next raid tier. I’d be surprised if that’s still a thing, but I’m sure to some degree it is.
I’d guess there is plenty of shady stuff going on. 
True.
My mind goes more to: there’s people in the world in “third world” nations playing a video game at a high level, selling content / gold for a living.
100% has to be some of that. Not that it would be a great living, but I’m sure if you could make $10-20 a day selling carries gold (maybe more), wouldn’t be half bad.
2 things. Firstly, I know rwf raiders burn through absolutely absurd cash doing split raids, buying consumables, and wiping thousands of times in their 20 man group wracking up repair bills. Your numbers came out to ~400 million, I’ll assume that those are right. Method claims to have burned through 480million gold during Sepulcher progression. Now, that’s a while back, but it’s about as good as I can get for numbers. These people aren’t winning rwf but they might still be wracking up a lot of expenses.
Secondly: Callouts such as this aren’t allowed. You saw a guild and think it might run afoul RMT practices? Report them, say why you think so in the field, move on.