It's not rare. It's just that there's not a lot of countries producing it. Mostly France, which produces and consumes two thirds of the world's production. And a few European countries.
So outside of France, it's very expensive, because it's imported. And even there, it's not something you'd eat everyday. It's a delicacy you'd eat on Christmas or new years' eve, or if you go to a really fancy restaurant.
Countries that import Foie Gras the most are Japan, Switzerland and Israel. And China is a growing market.
So, even if the U.S. were to ban Foie Gras altogether, it wouldn't hurt the production much. And the ethical reasons for banning it sound a lot hypocritical to me. PETA just threw a fit and some judges went along with it to get politically correct brownie points because it wouldn't hurt a lot of people locally.