In general, enemies in raids and dungeons drop significantly more gold than outdoor foes, specifically because we are assuming that the gold is going to be split 5, 10, or 25 ways. As player power rises over time, it obviously becomes possible to complete old content with significantly fewer players, such that the gold rewards become disproportionately high.
In the past, our only solution was to drastically reduce the gold dropped by legacy content across the board (e.g., Magtheridon, much of Karazhan, etc.). In Mists, we have a new system in place that normalizes gold yield based on the number of players involved in the kill. If a Black Temple enemy drops 100 gold today on live, and you kill it with a 25-player raid group in Mists, it'll also drop 100 gold and each player will get 4 gold. If you solo Black Temple, that enemy will also give you 4 gold. If you do it with 4 friends, it'll drop 20 gold and each of you will get 4.
In other words, the gold obtained from killing raid or dungeon creatures no longer depends upon how many people you bring, or do not bring, with you. This system does not apply to anything in the outdoor world.
You see, once upon a time, there was a raid called Molten Core. In its time, it took a raid team of 40 people. Bosses were set up to give each of those people a little bit of gold. Nothing to write home about, but ideally enough to cover repairs and that sort of thing.
Since there aren't selectable loot roles or anything like that for gold the way there is for other loot, the game had to do this in a rather roundabout way. The boss (or any mob, for that matter) would have its gold automatically distributed evenly to every member of the raid. This meant that if Blizzard wanted a boss to give each player, say, 5 gold, the boss would actually drop 200 gold and the game would give an equal amount to each of the 40 players.
This works fine until years later, when people discovered they could down those same bosses with just a very small group, or even solo them. The same 200 gold being distributed to one player instead of 40 was a bit much, especially when it got to the point where just about any class could faceroll it, so Blizzard nerfed the amount of gold given somewhat.
For Mists of Pandaria, though, Blizzard has a more elegant solution. Regardless of whether there's one person or 40, each player will get the amount originally intended to be given to each player (5 gold in our example). For a group of 40 still running Molten Core (do those actually exist nowadays?), this will actually be a slight increase in the amount of gold each person gets from the boss, compared to what they'd get now. For the person soloing it, however, the amount of gold they earn compared to what they'd get now will effectively plummet.
And what does this all mean from a gold-maker's perspective? Honestly, not a whole lot. I would hope you're not running old raids exclusively for the gold dropped by the bosses, as the gold per hour from that would be horrible.
That's not to say that running old raids can't be profitable. Things like Sulfuron Ingot, Lava Core, etc. still can sell for high prices if you're patient enough to find the right buyer. People can and will still make a profit from it, just without the little bonus of the boss gold
The only cases where I can see this making a difference would be when what you're farming is considerably more common, like cloth. With the added bonus of the boss loot gone, that's one less incentive to farm those things from a raid, as opposed to a five-man or even out in the world.
What do you think? Are there any old raids you've been running on a regular basis? If so, would this change make you stop? Let me know in the comments.