Another good thing about these Russian charters is that when passengers book and pay the flight, there is no ticket number issued, only their internal booking number. So, for example, if a tourist comes here, he/she doesn't have any return ticket number at the moment of entrance to DR. And the booking is confirmed and the ticket is issued only 24 hours before the actual departure from here.
There is a some kind of agreement between those airlines and DR authorities that their passengers of Russian nationality can enter DR without return tickets. So, when you import your Russian girl here via Punta Cana airport, you don't worry about her return ticket, she can board the flight and enter DR without it. And when you feel that it's time to change, you just buy her return ticket for $300 and bring another one.