The guy that doubts you can make over a thousand gold a day is probably like any other scrub that tries to make gold the hard way.
Let me rephrase that, making gold any way is hard. You won't find a legit way to make gold that is easy.
Now that you know it isn't easy to make gold, you want to go for the most efficient way to make gold.
Here are three ways I make 1000g+ a day without playing for more than a couple hours.
1. Get two gather professions. They are free to level and if you choose mining and herbalism (the two money makers) you can make a lot of gold while just leveling them. There is potential to make gold in production professions but they cost more money to level than you would make any time soon.
Go unholy spec so your mount is 20% faster and just chase down nodes and herbs.
2. At level 80, go back and do old quest lines. You'll get 10-15g per turn-in and they take very little effort to complete. It might feel like grinding but you can also gain rep and work towards achievements which involve finishing quests in specific zones. You could spend a couple hours questing and make 500g easily, both from gold rewards and from selling quest reward items.
3. Auto-loot everything that ever drops and use AutoprofitX (or a similar addon that sells grey items automatically to vendors).
If you have an addon that shows vendor values for any item in the game, you will notice that grey items that drop in raids often sell for a gold each or more. Don't ever leave grey items behind! Especially weapons. They can sell for 5-7g each.
These three ways are the no-brainer ways to make gold. By just implementing these strategies into your normal gameplay, you will notice a big boost in your gold stash.
Another way to make gold easily is to get Auctioneer addon and browse the AH for items that are below 50% PCT and purchase them, then post them for 70-80% PCT (as long as you're still below the lowest price).
One last tip: ALWAYS post auctions below the lowest price. It doesn't matter what it is. By the time the more expensive item sells you will be already on your way to making your next small fortune. Low prices sell fast always.
The lower the price the lower the PCT is, and the faster people will buy it up.