Beats me. It depends on a lot of factors. Where, when, how many people you invite, where they're coming from, how long they're each staying, etc etc. Many thousands of dollars would be required. Upwards of 20 grand, I'd think, easily. I mean, my ticket to Locarno was over $1200, if memory serves. So you figure a similar amount for whatever European guests you have, plus all the US guests' airfare and hotel costs, and it will mount quickly. And that's before any fees for print screening, possible hall rentals, and so on. So as mentioned, suitable backing and organization are must haves.
And no one should be contacting me regarding the venue, as I have no say over it.