I am wearing a free-of-payment signature, but what do you mean "they want to advertise for free (even if they know how to gain from it)" ?

Couldn't they simply generate smaller incomes, making them unable to afford $500 - $1000 / week for advertisement?

The number $500 - $1000 is arbitrary but not very far from reality. I 've seen campaigns paying more than 1M satoshis per week to the campaigners. Which means that the companies pay 1M + the manager's salary. In today's terms, 1M satoshis = $669

Perhaps bitcoin-related projects can't pay that much, even if the projects are great.