As an expert on strong premium prices, my opinion is the following. Ensure the exclusivity of advertising on your site and set an adequate price for it, create fewer ads that will be more expensive, but not too expensive if you have 90 ads for $ 10 = $ 900
monthly profits but if you had 60 ads for $ 30 = $ 1800
if you call me I can give you a good analysis that can bring you more followers and more earnings because 40,000 people is not too much.