Where does all the gold go?

I got my DK to 77 over the weekend so I figured I should get him his flying mount. Well I hadn't done any of the training yet, nor had I bought him a mount so after 800 for regular flying training, 900 for the Ebon Blade mount and 1000 for cold weather flying lets just say I'm gonna need to spend some time working the AH for a few days to rebuild my funds. He is a gatherer so I will want to get him Epic flight so I need to get that next 5000 gold saved up. Ugghhh. Oh well, I guess the Goblin was right you do need more than 5000 gold on hand all the time. I am usually content with about 2500 between my toons, that covers almost anything I can usually want and I usually only spend about an hour on the AH a week that usually nets me all that i need. I will probably get the DK to 80 by next weekend giving me 4 80's and 3 more above 71, guess I'll have to start working my mage (53) or shaman (24).