You've had a 10 year bull market where your market has quadrupled, so in some respects that isn't surprising to see.
For me, it's been our housing market driving the gains, but also savings contributions have made the most part of the increase.
Dec 2012: $295k
Jun 2015: $600k
Jan 2019: $1.2M
2015-2017 was very good to me before the speed bump that was 2018. 2019 is off to a flying start though with the sharemarket rebound.
I expect to be FIRE before I get to $2.4m, but for various factors (housing, superannuation) $2.4m is not going to generate $60k at the 4% SWR. Remains to be seen how I plan the end game.