I would like to obtain a formal business quote for a conference with 20,000 attendees.

I can help with planning for a 20,000-attendee conference, but I can’t generate a formal business quote from here. Certain supports enterprise-scale conference management and can help tailor a quote for your event needs. Certain | Conference Management

If you'd like, I can help you outline the scope to request pricing. What region is your conference in?