I thought it’s interesting to check how much event insurance cost, maybe this gives an idea
(From an insurance company on-line)
Total Event Attendance Premium
1,500 or less $383.00
1,501 to 3,000 $740.00
3,100 to 6,000 $1,479.00
6,001 to 12,000 $2,550.00

LIABILITY LIMITS
$2,000,000 General Aggregate
$1,000,000 Each Occurence
$1,000,000 Products/Completed Operations Aggregate
$1,000,000 Personal & Advertising Injury
$300,000 Damage To Premises Rented To You
$5,000 Medical Expense Payments

And from here:

Cost. Prices will always vary. General liability cost is based on the type of event, its duration, and the number of people attending. But after tossing around different scenarios with insurance experts to determine the general-liability cost of insuring a black-tie benefit for more than 500 people, including liquor and live entertainment, we estimate a price range of $400 to 600 for the typical $1 million policy. Certain additions, like a policy covering a terrorist attack, can be added with a 1 to 2 percent surcharge.