I'll cut to the chase since this is pretty straight-forward. While me and my friends were playing around in multiplayer, sharing our thoughts and observing features and the like; my friend and I stumbled across what is possibly the most hilariously game-breaking exploit I have seen in a while. It seems that if you use the quick buy on shipyards to purchase a ship, it will not cost you any money.
I watched in awe as my friend had managed to acquire a power of 750 at around turn 30 using this exploit by spamming constructors and colony ships to create an army of scout ships, and then colonized nearly every planet nearby while building a grid of economic star-bases. By turn 50 he had already pretty much won.
All 4 of my friends playing were able to replicate this exploit in single-player as well as in the multiplayer match, leading me to believe this is a problem with the game and not something we personally broke.
HOW TO USE EXPLOIT TO TEST FOR YOURSELF:
1) Click on a Shipyard.
2) Click the Quick Build button.
3) Select your ship and hit Buy using the Quick Build menu.
4) Free rush bought ship, as many as you want.