You failed to take into consideration one doing all their own farming of herbs.
The cost per card is only 12s (for the parchment).
I make approximately 400g per bag run (full bags 90 slots).
This includes about 1 50g card and about 5 20g cards.
I only paid 10g for 90 parchment.
I've turned a HUGE profit, including what I sell from my herbalism otherwise, including Volatile Life and Air, extra herbs, and Inferno Inks.
I urge you to check your sources.
There's an opportunity cost if you're gathering your own herbs. This cost is how much you're "losing" by not selling the herbs in AH.
400g / bag run => 90 slots => 90 stacks of Whiptail?
On my server, Whiptail is at least 30g/stack, so that'd be 2700g, or 1260g if you're on a server where they cost 14g/stack. I'm not sure if 90 stacks is actually what you mean though...
MFCs go for a bare minimum of 8g (when severely undercut) a piece on my server, and for a max of around 14g. If I list them in the AH though, I'm quickly undercut by some idiots who, instead of undercutting by 5%-10%, undercut by 30%+. I made around 1200 of them during my last gather run and have been able to sell around 200 for 2k, but haven't been able to sell the other 800 for days now. The market's currently screwed up by these idiots (they probably started selling once I barked in trade chat).
In other words, MFCs are in too high supply and low in demand. People (ie, idiots) will price them at anything as long as they make some profit from the herbs they bought, no matter how much time it takes them to mill, buy parchments, and create the cards.
There is also the issue of Darkmoon cards. I've run tens of thousands of simulations with a RNG and 120 cards is the average to create all four decks at least once each. About 54 cards is the average to create one of any deck.
120 cards/complete set * 10 inks/card * 1 whiptail stack/1.6 inks * gold cost/whiptail stack = 22,500g (assuming whiptail cost of 30g/stack and modestly ignoring the cost of Volatile Life).
On my server, volcano=~6k, tsunami=~10k, hurricane=~6k, earthquake=~3k. Complete set = 25k
So after spending time gathering 1200x20=24,000 whiptail, you make around only 2.5k in profit. Also, as you continue to make Darkmoon cards, the number of duplicates you have increases, thus decreasing the value/per card severely. MFCs are poop, Darkmoon cards are poop, and the glyph market is ?ber poop, so what's left for us Scribes?
If I've misunderstood you and what you say about making 2k-3k every 3 hours is true, then using the cards isn't bad at all. I really do hope this is the case. Otherwise, I'll be down to making less than 800g/hour on my server.