He's already got the season ticket money this season. The gate receipts from home fans will be quite small each home game say 2 or 300 hundred decreasing every game, including over 60's and kids so perhaps an average of say £2k per game + profits from program sales etc. I doubt that's going to hurt when he's willing to turn £9k+ down from the boxes.
Newcastle fans have been protesting and boycotting for years, but Ashley is still there.
If the owners won't go, it's practically impossible to force them out.
If we the fans do protest, it has to be covered by the media, and I mean TV, and the pressure has to be kept up.