when i did my characters, i leveled them 1 at a time. It just took a large chunk of my gold to do it and I nearly destroyed the herb market on my server... ( actually i did destroy the herb market... no one could buy herbs for under 50g for awhile because thats what I raised the prices to. Mind you this is pre wotlk so that was super expensive then )
but in the end, I made back nearly 10 folds with simple transmutes.