I believe the market is region wide, if that is the case assuming both those servers are in the same region you could put something on the market for a specific recognizable large amount of money on the character you want to transfer the gold to and then buy it on the character with the gold, would lose a bit to the tax but at least transfer most of the gold over.
Wouldn’t take my word for it though, that’s just what i’ve heard, worth testing it beforehand.