What do you mean by "special event"? That can mean many things. But here is a shortened version of the process:
1. Reach out to agent to check availability. You will want to send them the main details of the event which includes: date of event, who you want to book, where you want to book them (city and venue), and type of event.
2. If they are available for that date, then you will send over an offer. Your offer will have more details along with the price you are wanting to pay
3. If they accept your offer, then they will send you a contract and rider, and you will need to sign it and make a deposit (typically 50%) to confirm.
By the way, if your "special event" is a private event, the celebrity will typically charge more for this. As far as how much does it cost, it depends on many factors including popularity of celebrity, where you are booking them, when you are booking them, and other factors.
Here is an in-depth guide on booking: https://blog.bookingagentinfo.com/guides/celebrity-booking/how-to-book-a-celebrity/
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