Advertising is expensive, this is a lot cheaper compared to any ad service like Google Ads because.
Sorry, don't have paypal. I got banned for accepting donations without a tax ID or some bullshit they made up.
In a week you'd have 250,000+ unique viewers seeing your banner, how many click through is depending on how many you interest. I can't guarantee buys or anything of the sort, because it's simply a game of how you are able to interest people with your banner and landing page.