I wouldn't say movie tickets are expensive in the DR. In Europe a movie ticket costs you 6 to 8 Euros, in Central Europe about 5 to 6 Euros depending on the place. 2 to 3 Euros for the DR is not evry expensive.
Now, the DVD rentals - nobody does them. Maybe teh only ones are the pirates. You (people) buy the DVDs on the street.
Also the attandance is not high because of total price and the price elsewhere (read=street). It is usually because when the movie is in the DR theatres, it has already been in the theatres in the USA and most likely, already was published on DVD in North America or Europe.
Now, there are the sites like torrents etc and there is a flourishing business in the DR off pirated DVD and CDs. The wholesalers download and copy these movies from NA and sell them for about 30 pesos to street guys, who in turn sell them for 60-80 pesos (depending on how many intermediaries and profit sharing by others is involved).
So why would anyone pay 120 for DVD rental, or 300 pesos for a theater ticket (for a couple) when they can pay 60 pesos and watch the same movie at home. For the money they save, they buy chips, soda, chimis, and other stuff to enjoy during the movie and still they pay less. Very few people go to theatres just for the sake of "theatre experience".