Er, I wouldn't judge an entertainment by how long it is, tbh. Just because Wagner's operas go on for 2 days, it wouldn't make me pay more for the ticket than a nice Verdi!
I also don't think many people would be impressed by the argument that they should pay more for a ticket to see a two and a half hour film, than an hour's circus show. And if the NT started to do Shakespeare's plays unedited and charge more for the longer versions, no-one would go.
Surely you judge each entertainment on its own terms, not on how long it takes versus another form of entertainment.