This is why they push the season pass before the game even launches, guaranteed money, just look at trophy percentages for main game completion compared to the easiest dlc trophy, it'll usually be in the 1-5% range.
I've bought complete editions and never even beat the single player game let alone the dlc.
I don't usually finish a game and finding myself wanting more, if anything I could do with games being shorter and cutting the fat.
Going back to buying dlc/ gold editions at launch, there's probably a like a quarter as likely to buy dlc after I buy a game then before I buy it.