It is pricey. In only bought a 330ml, but I'm glad I did.
My French isn't great, but if you click on the link in my post to the BFM site, they mention cutting old beer with young bitter beer:
Je déguste et me viens l'idée de couper cette vieille bière avec la même mais très fraîche et bien amère.
Says something like: I taste it, and the idea comes to me to cut the old beer with the same beer, but young and very bitter.
They also then go on to mention a conversation with Yvan de Baets, who told them that this was an old Belgian practice.
(I think they also make fun of the US beer market a bit too, saying they called it "historical" because they were sending it here. But I might be misunderstanding it.)