A ship christening costs roughly €200 to €500+ per person ex. VAT for 250 to 500 guests. For 500 to 1,000 guests you should count on roughly €175 to €450+ per person. For 1,000 to 2,000 guests you should count on roughly €150 to €400+ per person. All amounts excluding VAT, including venue, catering, entertainment and production.
A ship christening depends heavily on the scale of the vessel and the desired publicity. There is a big difference between the minimum version and a full-scale production.