A prime slice of fatty, creamy otoro — belly-meat of Bluefin tuna — isn't cheap. These days in Tokyo, you can expect to pay at least ¥10,000 ($100) for a goodly portion of the stuff.
As supplies dwindle, prices of tuna have been going up, and if fuel prices continue to rise — meaning that year-long fishing trips by ocean-going boats out of Japan become less frequent — then the price of the fish will rise further, too.
But I think tuna should be even more expensive.