International (and all intra-EU) flights are protected by the Montreal Convention 1999 (MC99) which limits an airline's liability for loss or damage to about SDR1300 per passenger. This is the extent of airline liability, unless you can prove that they did so intentionally.
While, in theory, you can get Excess Valuation - find me an airline employee that has any idea what you are talking about, I'll give you a free beer.