Well, electricity is a psychological barrier. They don't cross it because they've walked up to it and been shocked. You have to set up a training with them to do it, so that they get shocked - put up the fence and then put something tasty *just* on the other side so they have to reach through. That usually does the trick. If they are really determined, most CAN fly over but if they have been shocked once they usually will not.
72" sounds pretty good to me, most would not go over that. If one does, what you can do is catch that one, and trim the feathers on one wing. You want the feathers short but don't cut down into a blood feather. (They are not clear, like a mature feather. They are dark red or just dark on the shaft.) This may have to be repeated when that bird molts.
As far as cost and maintenance, it's hard to say... perhaps someone will chime in? I think I have two chargers now that don't work anymore. Personally, I prefer a fence that is just a plain fence, but it can really depend where you are and your own personal feelings. One thing about electricity! You can bet that no predator is going to try and just bull their way through! It does deter dogs and such really well.