I did bite the bullet and buy 4" pots from Charley's Greenhouse (discounts start at qty of 90), but for 2 dozen plants, Styrofoam or plastic cups with holes drilled in them is probably perfect for your needs.
Of course if you start growing other crops like cucumbers and squash from seeds you start yourself, or flowers, etc. etc. pretty soon you'll find a reason to buy 4" pots.
