After a hour of performing this I can get about 3700g usually. I tend to sell the plants for 3000g and the rest comes from disenchanted greenies and prospected adamantite ore mainly.
Bring Me A Shrubbery!
You will need to focus on one item only: Sanguine Hibiscus. This is obtained from Underbog instance in Zangarmarsh. It's dropped by almost every mob in the instance and can also be picked up from the ground while there. Not even herbalism is required! They drop from both Normal and Heroic modes. The instance is easily soloed by a level 70+ person.
You can get around 30-70 Sanguines from one run if you loot every flower and kill all non-naga creatures. In less than two hours of farming you can obtain hundreds of them! Note that you can enter only 5 instances in a hour.
Felicia from wowhead has posted an excellent farming tip if you're not familiar with the instance. Check it out. There's even a map with the spawn points marked!
Got the flowers! Now what?
To sell them efficiently, create an interesting macro and sell your plants in the trade channel. No one will bump into them in the Auction House unless they're specifically looking for them. Here's an example macro! Use it as a template and modify to make it look nice enough for even yourself to "buy it".
WTS 260 x Sanguine Hibiscus - Enough to get you exaltedCheck how much the flowers go for in the Auction House before deciding a price. Usually there's only a couple for sale so you can ask for thousands easily! You may also remove the price tag and let people give you offers so more people will whisper you in case the price is too much for them.
with Sporeggar! Get the Diplomat title + Sporeggar Tabard
and the Tiny Sporebat companion pet for only 4000g!
The amount of flowers is a little lower with the correct guild perk or human racial, so offer cheaper deals for guilded people or humans if you wish.
This is a nice gold maker in my opinion as it only takes a hour or two to get enough flowers, and you don't need to spam your macro long before a buyer is found. I'm always the only one selling these so I don't have any competition either.. yet!