Replying to myself:
The excellent and free Mill Base:
http://katar.weebly.com/blog/millbase-for-scid-update2
chooses to bypass non-master games, and as a result is 1.74M in size (average ELO 2,417).
This also presupposes SCID vs PC, which, among other things, allows merging two or more databases without those annoying dupes. It even standardizes a lot of the players with variant spellings etc.; functions that I've found to be unreliable in ChessBase. But the latter is my preference for data consumption.
** Edit June 2019. While not current any more, the database had the right idea. Adding new games where one player has Elo > 2400 can replicate this if one has the time. **
I've just paid for a ChessBase license and set it up, but haven't gone so far as to purchase the Big Database, which typically is another $USD70. Instead I've been able to use and embellish a database which was bundled with Fritz, and adding over time the TWICs. Currently I'm good for 3.76M games, with an average ELO of 2,284, and for a trivial cost.
I'm told (keep in mind I am a complete patzer so respect to any listed player there) that non-master games (that is; below ELO 2,200) may not be as helpful? Eliminating those however more than halves my game count. That said, the resulting 1.78M games is nothing to sneeze at.
My call is to those that do own a commercial database; for example the ChessBase Big Database, which I'm told is 6.4M games. Is this made up of an overwhelming majority of non-master games? What is the average player ELO of a typical ChessBase commercial database? And would having a much wider variety of openings/middlegame data be useful for aspiring ChessBase power user/s, even if sourced from lower-ranked players?
** Edit June 2019 : if anybody is interested, I have found more utility with smaller and stronger (~ 2M games) databases over the larger ones. As I suspected, and indeed noted everywhere, the larger databases are not deeper with theory, and at my level opening preparation (if at all necessary) need only be around the main lines. Openings I've encountered usually are not found in a database of any size... probably for a reason. There are opportunities to use the larger database anyway by pressing Enter, (which requires the Playchess subscription), for what that is worth. **