Sony unveiled the 6.4" Xperia Z Ultra just a few hours ago but there was no info on the pricing at the official event. Fortunately Sony Netherlands shared the European price in its local press release.
Sony Xperia Z Ultra will become available worldwide by the end of Q3 this year and you will be able to get one for €719. That's quite steep, but given the kind of package it gets you, probably reasonable price tag.
The Snapdragon 800-powered water-proof Sony Xperia Z Ultra phablet will be available through quite a few carriers as well. You will most probably be able to get it even free if you opt for some of the more expensive 24-month contract. The UK carrier Three was the first one to announce the availability of the Xperia Z Ultra on its network later this year.