Since gold exchange wasn't included in the base game and Torchlight 2 has a very well done system of gold sinks, this is definitely a way to bypass that mechanic and twink out your low level characters earlier. But it can also be a way past the frustration of hitting a wall because you're low on resources. It's up to you, the player, to use it wisely and not abuse it to your own detriment.

It's come to my attention that with Barter skill or some mods like Synergies that modify sale prices the player could easily abuse this by buying and reselling on the same character to accrue unlimited gold. Again, this is kind of silly because there are a lot of gold cheats as easy as pulling down the console.

But if it improves immersion and helps the mod feel more "balanced", I would be fine removing the ability to buy and sell goldfish at the same base price of 1000 gold, and instead use the game's existing mechanic which makes buy prices 4x higher. The sell price would remain at 1000 but the purchase price would increase to 4000 (2000 in Synergies, possibly less with the appropriate Barter skill.) So it becomes another gold sink. Let me know what you think.