Unless the ev1l pirat0rs actually compiled a different version of your app in order to give it away for free without those messages (which seems unlikely given there's absolutely no incentive for them to do so) you'd make a pretty penny through the sheer volume of users.
Imagin busking to an audience of 1 million people, all equidistant from your guitar case with one dollar in their hand?
The scale at which digital distribution allows piracy is the same thing that will make you money: you have free distribution to millions of people, just figure out a way for them to voluntarily give you money and you'll be sorted.