How much you make from a Spot highly depends on the time you farm, how good you and your Class are at farming etc. For Example, farming turtles at Launch of Pandaland and turn their Meat into Ironpaw tokens was very profitable. Doing so now where a lot of Ironpaw tokens are in the game already, and when the Turtles and their meat was nerfed, won't give you too big of a profit.
Another Example were the strong Bracer Enchants: At the beginning of the Expansion, only very few Enchanters did all the Dailies to get Enchanting Recipe reputation every day, and of those only a few bought Hozen Piece pipe for additional reputation. How few you ask? Of the 120 000People of our Server, only two offered Bracer Enchants. They made over 6000Gold profit with a single Enchant, although they propably spent over 50 000Gold for each Hozen piece pipe.
Nowadays the very same Enchants only make one or two hundred Gold profit if you sell them.
What's interesting is the Gold inflation that happens at Expansion's launch which increases both Gold earned and Gold spent, so for Example Mining at Launchday could also net you 40 000Gold per Hour but Darkmoon Trinkets costed over 100 000Gold. Today Mining gives you maybe 2,5-3000Gold per Hour and you can buy Darkmoon Trinkets for 6-8,500Gold so the People of Launchday could not necessarily afford more Stuff than the people of today.
About how to get Gold: The basic Gold is generated from Questing and killing Mobs, about 400-700g per Hour on max Level. Generating more Gold is not possible: Blizzard reduced Gold drops of all Bosses and Mobs when introducing AoE loot. And the majority of players never reach max Level so an average Player earns maybe ~~200g per Hour or even less. The only way to earn more Gold is extract it from other players. Some tips have been listed here, most boil down to : Farm the Profession ingredients currently in demand most and/or use Professions to create stuff that sells for more than the ingredients cost.
To get even more gold than that, one must be pretty clever and use strategies that as few others as possible thought of. The strategies are shared with few people because the more know of it, the less is earned. Many times, they are also bleak, unethical, or un-fun in many ways. So if you want to be a Millionaire like me for example, then be prepared to be bored and sad a lot, and to live with the guilty conscience of having made others poor