~~~~
Wait a sec. When you say "four-digit salaries" are you talking in terms of USD amounts? Because if so, I have to tell you that I remember the Yobit campaign from years back, and they paid 30k sats/post, but bitcoin was likely below $1000 at the time and unless you had 100 accounts enrolled in the campaign (lol, I'm sure some people did) there's no way you were making that much money.
I would also mention that campaigns are still around, after all. They must be beneficial for the businesses that run them, so I'm not sure why the rates have dropped so drastically. Do people gamble on crypto casinos less? Are there fewer exchanges coming into existence? Most of the bitcoin-paying campaigns from back in the 2015-18 era weren't for ICO projects, and it's not like enthusiasm for crypto has died down at all, so I don't really understand it.
Yobit used to pay
BTC0.006 per day and that amounted to
BTC0.18 per month. When the BTC price was around $1,000 per coin, it amounted to around $180. So you are right in that case.
But I remember the case with Prime Dice. They used to pay as much as
BTC2.4 per month. And that was when BTC was trading at around $1,000 per coin in 2014. So they were actually paying four digits. Too bad that the campaign lasted for just a few months and after that they folded up.
Then there were a few such as BestMixer, WOLF.BET and Ethexbet, which used to pay decent amounts in 2018-19. Mostly in the $400-500 range.