This is not the first time that I see people refer to money as "box" ([see here 0:12][1])

I searched in my dictionary and I didn't find a meaning like that, so I think about two options: 

a) Maybe there's another word which sounds similar but is written differently.  
b) It's the word and it's not in all the dictionaries  


  [1]: https://www.youtube.com/watch?v=sRDGUz5I4Ms