Though KRyan's answer is absolutely correct, I'd like to elaborate on having all three stats at 30. Just for completeness. It may be impractical but it is definitely not impossible. Magic items with +6 enhancement bonus would cost you 36,000 gp per stat (Periapt of Wisdom, Headband of Intellect and Cloak of Charisma), +5 inherent bonus would be either 25,000 XP per stat (5 consecutive wishes) or 137,500 gp per tome (Tome of Clear Thought, Tome of Leadership and Influence or Tome of Understanding wondrous items). Thus you have +11 total to each stat. It means you need only 19 in each stat at the start.
A 17 in a stat plus racial bonus can give you 19 in one of them. The rest you'll need to raise through bonus points at levelling up. 5 points at level 20 will allow you to start with 18 and 15 or 17 and 16. Or alternatively you can raise a 16 stat to 18 with racial bonus and use one bonus point on top of that, then you'll need other two stats at 17 and 17 or 18 and 16 initially. If you happen to have two stats at 18 (exceptionally lucky roll if you roll stats) you can have the third one as low as 14 to spend 3 bonus points and +2 racial bonus to get it to the required 19.
To sum it upTo sum it up you need stats at 17,17,16 or 18,17,15 or 18,16,16 or 18,18,14 before racial adjustment and either spend 520,500 gp or 108,000gp and 75,000 XP total. Since you are expected to have 760,000 gp by level 20 (table 5-1, Character wealth by level, PHB p.135), it is not cheap but affordable.