Targeting using cumulative gains curve

Consider a population of 10 000 potential donors and 1000 targets that you want to write a letter to ask if they can donate 10 Euro. You created a model with a cumulative gains graph as given below. Sending out one letter costs 1 Euro. Assume that there is 4 000 Euro budget, so you can send letters to the top 40% donors with most potential to donate. As the targets will donate 10 Euro, reaching a target results in 10 Euro incomes.

How much profit do you expect to make?