I'm looking forward to his answer to this. But I would guess it's something along the lines of:

-Society spends 2B gambling

-Govt receives .7B tax revenue and spends it poorly

-Game owners pocket 1.3B which disappears forever

-Cost of increased social safety net, suicides, etc.

VS

-Society spends 1.5B on goods and services rather than gambling

I don't think it's fair to count the venue, staff, etc., if the same money would otherwise be spent on other goods and services.