When I say metropolis-wide party night I mean this: picture your run-of-the-mill festive fantasy village where food and drinks are in abundance (and not necessarily cheap stuff), musicians and staff work for hours and whatnot. Everything provided by a single PC. Now, how much could it cost to fund such an event for, say, ~20000 people (rounded up to account for extra expenses)  ? Even a rough estimate would be alright.

How much would it cost for a PC to fund a metropolis-wide party night?

When I say metropolis-wide party night, picture your run-of-the-mill festive fantasy village where food and drinks are in abundance (and not necessarily cheap stuff), musicians and staff work for hours and whatnot. A single PC provides everything. 

Now, how much could it cost to fund such an event for, say, ~20000 people (rounded up to account for extra expenses)? Even a rough estimate would be alright.