Ok, this is one of the most scientific and economic analysis I've ever seen on Starcraft 2
Top level players are renowned for their ability to rapidly spend the resources they collect, and it has often been joked that an ideal player would never float above 400 minerals. But do top level players actually approach that figure, and how does their spending vary as their income increases across the game? One might guess that average unspent money is approximately a fixed percentage of average income. However, the data tell a different story.
Surprisingly, there is a very close to exponential relationship between Average Unspent Resources and Average Income. This means that for Grandmaster players, every time their average income increases by 500, their Average Unspent Resources approximately doubles.
There's a whole analysis with graphs, formula's and tables comparing the spending and building differences between the different leagues.