As people have said above, the ticket prices are extremely high, especially for someone who hasn't been exactly relevant in recent years. I don't know what they were thinking.
The main problem is the price for sure. I don't think the venues are bad per say, because if she had cheaper tickets and a hit this era she would have no problem selling them out.
And "production delays" would be an awful excuse because she is touring nearly exclusively in amphitheaters, there is not much her team can do with a stage.
It's not that easy having a great selling tour nowadays, for the fans and general public it's not only about the ticket prices but also hotels, tickets plane and a lot of other stuff and it's becoming really expensive.
People do that only if you're the hot thing of the moment with several hits or if you an established legend-act when it comes to tour like Madonna, Beyoncé, ecc, but if you are out of the game for like 10 years and without hits... Sis...
Well she has no demand to fill arenas with normal prices so even less chances with those expensive ones, what was her team expecting? Hope for her fans she doesn't make a Janet too.