It is VERY important to check and triple check before you place an item for sale. Whether you’re using a posting string with TSM, using Auctionator, or even just putting your items up for sale using the base UI.
When you use the base UI, a few things happen depending on the item / if there are any for sale. If others are up for sale you’ll price match the last one. The auction house works on a LIFO method “last in first out” so there’s no need to undercut that auction.
The thing is, there are some ‘less desirables’ out there who want to make sure you lose gold. Unpopular opinion here, but I do not condone what these goblins do. They put up ‘bait’ in the auction house. Then the next person who isn’t paying attention comes along and matches their prices – and they attempt to buy out those people. Then they can resell the item for a profit. Personally, these are the sort of goblins that give other goblins a bad name. I don’t think that gold making needs to be done by tricking others or fooling them out of gold. That opinion isn’t shared by everyone, which is fine. It’s simply not a method I use or believe in.
Now, it IS common for people to just naturally make a mistake when putting an item up for sale if they have no idea what the value is – especially if there are zero already for sale. If the item has no others for sale, for example, the default UI will commonly use a very low price from Blizzard. In some other cases people have used their TSM strings to post very expensive items for vendor value (when there are no regional prices, for example, because the item is too new).
You don’t HAVE to post at the default number given – always make sure you check so that you’re not being baited into posting for under the value. In the case of the fluid above, they actually vendor for 62 silver – not a huge amount, but when you bait all day long and occasionally catch thousands of these things being posted, it can apparently pay off.