To complete IMBA, game mechanics are tweaked to ensure adequate pace in IMBA games.
Structures and creeps receive periodic upgrades to their stats every minute of game time, starting from the first minute onward. Creeps, Summons, Towers, Barracks and Ancients stop gaining upgrades at the 30 minute mark in the default upgrade speed setting. You can choose to make these upgrades happen faster, by selecting Fast (upgrades every 30 seconds) or Extreme (upgrades every 15 seconds) in the game options as a host, and the maximum upgrades would consequently be reached at 15 minutes and 7.5 minutes respectively.
100 gold + 25 * hero level + 20 * game time