Ehhh, not really. If showing 10,000 people an ad costs you $10 and even one person made a purchase off that, you’ve paid for the ad buy. Internet ad conversions are considered unbelievably excellent if 1% of viewers click on the ad and 1% of those people make a purchase.
Also, if you don’t advertise, then your competition that do advertise are going to eat your lunch.
Gabe was talking about the making of Half Life, back when you shipped your disc and that was that. And the game was, apparently, crapola.
Same kind of deal with the original Deus Ex. It was a spaghetti of poorly interacting systems until the devs were able to make it all click together.