I agree that flying mounts are probably the biggest gold sink in TBC. I remember spending a lot of time farming herbs and ores just to save enough for epic flying. Gathering professions were definitely the most consistent way to build gold, especially early in the expansion when material prices were high.
The Auction House was another great source of income if you kept an eye on market trends instead of selling everything immediately. Planning major purchases instead of buying every gear upgrade while leveling also made a huge difference and if you like mobile gaming visit Cb777 apk download.