With any business it's all about profits. The bigger the profits the better...... That aside, $5.99 for the convenience of a 24hr PPV is a bargain when you compare what it would cost to go to a movie theater to see a movie.
Absolutely it is about profits. But is DirecTV maximizing profits at $5.99? Would they sell 2x as many at $3.99 and make more profits? Since we don't have access to the numbers, we can't say. But given that most people on this board, many of whom are big fans of DirecTV, think the price is too high, I would guess the average sub thinks it is too high.
Also, PPV are not necessarily competing against the theaters. Somewhere in my brain I want to think that back when I first got DirecTV, PPV's were available before the movies were available on VHS. Not a huge gap, but a gap. Of course back then the time from theaters to VHS was a lot longer.
So PPV's are competing mainly against RB and BB and NF, not the theater. In that comparison, they lose. Maybe a slight bump for spur of the moment convenience, but not for those who can plan. Or who have fast enough internet to make streaming effective.