[majewsky]

Economy has functioned by word-of-mouth for millennia. Ads as an industry are relatively new (maybe 300 years).

(Sure, word-of-mouth is a form of advertisement, but OP clearly refers to the ad industry, so I'm going with that meaning.)

[gtt]

Those millennia world was mostly in Malthusian trap.

[jhall1468]

How much are you willing to pay for every advertising supported site you use?

[milesvp]

Apparently there was a study related to this this recently.

http://timharford.com/2018/05/how-much-would-i-have-to-pay-y...