There's no guarantee of a good crowd anywhere. Certainly Auckland has had some weak crowds over the years. But the Eden Park deal is better these days?
Eden Park are desperate for customers these days. A year or two back there were serious discussions about having the Auckland Gaelic football grand finals there. (Men and women. My club was riding high at the time and that was the closest I will ever get to playing a game at Eden Park.)
Article pre that very big Victory crowd that they got in Feb 2019 - when yes everything luckily came together (mid summer, Nix on a winning streak, almost local Fijian Indian boy Krishna scoring for fun etc etc)
https://www.stuff.co.nz/sport/football/a-league/110520744/wellington-phoenix-raise-possibility-of-record-crowd-for-their-return-to-eden-park
"After that last match, in December 2014, where the Phoenix only posted a crowd of 11,051, short of the 12,000 they needed to break even, Dome said Eden Park wasn't an attractive place for them to play any more, but last week he told Stuff that had changed under the leadership of chief executive Nick Sautner.
"He's making efforts to make the business model more attractive, which to a certain extent is good. It's good for us in that it became an option again. The offer that was put on the table was certainly much better than it has been in the past. Put it that way."