movies cpa conversions

i have a new movie site i decided to promote relevent cpa offers .you know offers that requires you to register and enter your visa card number to complete registration free of charge for sites like nitfilx .

i got a sale from us ,i got 19 dollars for it.thats very good
i decided to run popunders on my site containing the cpa offer and see how many visitor required to get a single conversion .
i have always seen pop ads like popads.net networks promote movies cpa offers that must be profitable .it ran all the time from years ago ,if it was not profitable ,it would stop years ago .
how many average visits required for popunder cpa offer in a movie site to get a single sale?