Just as bitter and nasty tasting as freshly squeezed orc would be. So is the idea of a deal gone horribly wrong. The more active trading that a gold goblin will do, the more apt they are to run into a deal that is too good to be true.
There are two things that you have to consider when approached with one of these huge deals. First is it for personal reasons. Someone offers to sell you the [Reigns of the Ultimate Dragon]. It's the one that you drooled for years to have the item advertised in trade chat selling for a cool 350k. You must have it, your life will not be complete without it in your inventory.
But take a deep breath. 350k is a lot of gold for something, that's almost 6 months of your crafting, listing, selling, running around getting every little bit of gold you can. Very rarely is 350k the amount that someone would take for that. And worse, it might be something that was duped recently on another server. Not really your problem, til blizzard finds out and yanks all your new toys away.
This is an extreme scenario, but it does happen from time to time. Big ticket items demand to be looked at time and time again. A level 1 having a big large ticket item should bring up the alarms in your gold goblin system.
The second things to look at is the resale value. If it isn't for personal bragging rights, then you should be looking at the potential profit or loss on a sale even closer. 100 inferno rubies for 100g a piece might look like an awesome buy. But the inferno ruby market has been losing steam quickly. Less gear being gained and less need for big gems. How much can you resell the item for legitimately? Will it be something to sit on til more people have excess gold to spend? How much space will it take up in your bank, will it lose value or even gain value. Five minutes of time can save you a lot of aggravation just by considering whether the purchase is worth it.
So before going to squeeze an orc, think about whether that orc will really appreciate it or will he come back to bite you.
Good Luck and Good Hunting