just a shot in the dark here but I'm gonna guess maybe it has to do with possible RMT? So by reducing the cap it will stop people from amassing hundreds of millions and selling them from a 3rd party site to new players who are overwhelmed by the high prices when starting. It will make it more achievable for them to get ahold of stuff with out resorting to forking cash over to some other guy and not SE. It should balance out the market to a more reasonable economy. 1 million might be a bit low imo, but 1 billion is way to high for sure. I would say somewhere around 4-5 million would be good.