We went recently, Hawks versus Swallows. It cost about $30 for two adults and two children (these are the cheap seats, so make sure you get there early to get good seats). You can get tickets from the stadium or Lawson stores. The facilities are fantastic. The roof was open for most of the game, started to drizzle and they closed it, this was quite a spectacle it's self.
For food there is Macdonalds, KFC, hotdogs, Subway and more traditional food, and of course beer!. Kids run around with little kegs on their backs, so no need to miss the action (about $5 -$7 a cup). Everything inside the stadium is dearer, though no worse then any other sports ground in the world. We've been a few times and don't recall ever waiting in a line for anything.
From Tenjin take the subway to Tojinmachi and walk down the riverside. We took the bus from across the road from Nishijin station, but its not far to walk.
There is also a shopping mall (Hawks Town) next door, shops, restaurants etc...
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