A New Year's drinks event or reception costs roughly €125 to €175+ per person ex. VAT for 250 to 500 guests. For 500 to 1,000 guests you should count on roughly €110 to €160+ per person. For 1,000 to 2,000 guests you should count on roughly €100 to €150+ per person. For more than 2,000 guests you should count on roughly €75 to €100+ per person. All amounts excluding VAT, including venue, catering, entertainment and production.
A New Year's drinks event is informal and relatively short. Plan well in advance: in January the diaries of many caterers and venues are already swamped.