AAA: COD, GTA, Assassin's Creed series, Mass Effect, etc. around 5 million sales to break even.
AA: Dark Souls, Metal Gear, Uncharted, 2/3 the development budget of AAA with one tenth of the marketing budget around 1.5 million sales to break even.
A: Anything by Platinum or Grasshopper, niche titles. around 150,000 sales to break even.
B: shovelware???
anything lower is probably indie??