Thanks for the chapter, Team Duwang!
Actually, I think Baku used the 990k as a trick to see if he was against some kinda freak who'll be able to count the book's pages.
I mean, in normal circumstances, knowing there's not enough bills, Hachina should have refused the game, saying "that's not 1 million yen. Goodbye". But by staying silent, maybe he made Baku think he was not able to count the bills?