Having multiple accounts for profession alts is
buying gold. (Bring the flames.)
No one really cared about mutibox crafting in TBC and WotLK because the bulk of your gold still had to come from other players. There were limits with what you could do with prospecting or milling, and profits from transmuting epic gems was kept in check by the free ones coming in from Battlegrounds and Heroics.
The high vendor prices in Cataclysm, however, allowed players to sell directly to the NPCs, with their infinite gold and no threat of market saturation. Now more accounts translates directly into more gold. More dollars sent to Blizzard meant more gold in your account. It's Pay-to-Play, just billed through a different department.
How come we didn't see all of these multibox millionaires in the last two expansions?
...you should mentally divide a player's wealth by the number of accounts they run: A single account with 500k = A double account with 1 million = a full multiboxer with 5 accounts with 5 million.
It's worse than that. We have downtime when we play, the multiboxer does not. We quest, we raid, we grind faction rep. If we prospect for an hour and play for an hour, we get one hour's worth of prospecting done. If the 5-boxer does the same, he gets 9 hours of prospecting done as his other accounts continue to churn through mats during his "downtime". I'd divide gold totals by double the number of accounts. (My opinion is that a 5-boxer with only 5 million gold at this point in the game is screwing up badly somewhere.)
As for RAF'ing 20+ Alchemists
do these people have any friends? Girlfriends? I'll presume they are male.
Making 50 alchemists on 5 accounts would be faster than making 10 on one account. Between RAF bonuses and always questing in groups, the actual playing time needed to level up characters in batches is much less than soloing one character at a time. It's not a question of who has less of a life, it's a question of who will pay Blizzard the extra hundreds or thousands of dollars for the extra accounts.
Having 5 prospectors instead of 1 - or 50 Alchemists instead of 10 - doesn't mean that person is 5 times more gooder at making gold. It means he's paid for 20 game boxes instead of 4 to set it up, and he's paying $75 a month to keep it running. Nothing more, nothing less.
(Disclaimer: My now-closed 2nd account consisted of a level 65 Scribbler used for crafting inks during Glyphmas, and a half-dozen no-profession glyph posters. I had the mats stockpiled for a multibox army of crafters when Cataclysm launched, but some naval gazing led me to a different Path.)