Look at the round numbers that are coming in and going out -- always multiples of 12,500 -- the same a s block reward.

I do not know for sure, but the simple explanation is that this is the address of a large pool and they mine many blocks per hour.  They hold blocks while they mature and then payout blocks to miners.  That accounts for the pluses and minuses happening on such a regular basis.  +87,500, -75,000, etc.  An increase in winning blocks today over when you looked 3 days ago could account for a 2 million increase. 

I doubt that the price would have slipped through the low 40s if someone was accumulating that many per day.  But if someone is accumulating millions, then they are probably doing so with the expectation that the price will appreciate and they can sell for a good profit.