The 1851 Inspiration is available in several outlets through Australia, but if my friend has seen it for $150, he should buy it, because I've seen much, much higher price tags on it.
The point made by several above is correct....
Macallan put out their replica series, only to find well and truly after the event that their source bottlings were fakes.
Since they no longer could hang their hat on the "replica" mantle, they elected to coin it "inspiration" instead.
So...the above is all to do with what's outside the bottle. I guess the most important thing is what's inside the bottle?
THe answer is....not much. I've tried it, as well as the original replica bottlings, and whilst they're pleasant enough whiskies, they certainly ain't worth the extra $$ from a tasting point of view. By all means, pay the extra if you want it for its collectability, but the whisky inside is nothing exceptional.