Let me preface this by saying: I can't say for certain that this isn't my own stupidity (I really doubt that it is), but I wanted to post this in case someone else had the same problem.
I was using the Auction House in steel canyon today, posting a Miracle: End/Heal/Absorb Recipe for 17,000,000; and it didn't post. This ate 850,000 inf which is not an insignificant amount for a low level toon. It came up with a popup asking if I was sure I wanted to spend that amount because of the relatively large transaction fee. I clicked yes.
When nothing changed status, I removed them from WW to see if that would help, and it let me take the recipe back into my inventory. I checked back later in the day to find that another item posted for the same amount. A Second Wind that obviously isn't going to sell.
Again, I can't say for 100% certainty that this isn't just a colossal user error, but I thought I'd put this on peoples radars in case there were similar issues stemming from the game assigning the wrong item the trade value when the confirmation popup occurs.
Never got that inf back either way. I'm getting mixed signals in chat about if you're supposed to get that trading fee back, but I'm far more concerned about the potential bug then the loss of money.
Reuninion Server, playing from America, so perhaps lag had something to do with it.