The OP's point is that the exchange rate went down since the announcement.

Yes, a lot of people can't comprehend how much 18k BTC is, so news articles put that number in fiat value at the time it was lost. As price have huge fluctuations like it does now, so does that fiat value.

so they can donate the 1.6m USD to charity! 

It doesn't matter what the value of the bitcoin is when they are sold by the hacker(s). All that matters to bitstamp is the cost to them to repurchase the 18k BTC to replenish their reserves

2 pizzas?

Well, he says less money stolen, so I dont think he means the current price.

Depends on the toppings, you can get 2 small with ocean pearls and 1/2 carat diamonds, or 2 party size with gold leaf and freshwater pearls.... no anchovies.

Whatever the reason and amount is, this is the kind of news that puts reputation and value at risk. So new invests are hard to come by.

IMO it really doens't matter. 18k BTC is still 18kBTC. What really matters is bitstamp's replacement cost of the coins that were stolen, not the value of the stolen coins at some arbitrary time