I think 4K keys is about right for going from 0/6000 friendly to exalted. It is possible to grind to 5999/6000 but only from select mobs that give just 2.5 rep each. I heard about 5K keys to go from 0/3000 neutral to exalted. There is some RNG involved, as you randomly get one of six TBC reputations when a friendly guy is spawned. About one out of six (1/6) keys will spawn a friendly that gives reputation, and then only 1/6 of those will be the reputation you want. Whomever said 1k keys is way off. To put it into perspective, I got a total of about 22,000 CE rep with 2000 keys. Now considering I was getting 550 rep each time (with 10% bonus), that's only 40 out of 2000 key turnins resulting in CE rep (about 2%).