This was something I was discussing the other day actually with another trader, although I was more talking of sponsoring such an event as by that time my UK exchange will be in full swing and have been operational for several months. The sponsorship would cover the venue costs although to be worth it from a business perspective you'd need some high profile guests attending to give it prestige.
That sounds like a smart move financially, but there are some obvious advantages to making it a private (and privately funded) party. Basically: we can do what we want, and invite whomever we want