Originally Posted by Cary Grant
Yup- the prices to manufacture 375's (the bottle itself) whether champs or regular wine is significantly higher.
First, half-bottles of champagne are so expensive because there is actually no such thing. Nor does champagne "age faster" in half bottles because, properly speaking, it doesn't age in half bottles at all. Rather, I should say, it isn't cellared in half bottles. Once it is shipped out to stores and warehouses, what happens to it can't properly be described as aging. It's more like elder abuse.
Champagne is cellared in full-sized bottles or, occasionally, magnums. When the label wants to sell splits (half bottles) or the little quarter bottles that trendy clubbers drink using a straw, they decant the full-sized bottles into smaller ones. All this extra effort adds considerably to the cost. To put it another way, if they could only sell you splits at half the price of a full bottle, they wouldn't bother making splits. It wouldn't be worth the trouble.
The same thing goes for the larger bottles. Some magnums are cellared but they are also sometimes created by dumping two full-sized bottles into one big one. Everything bigger than magnums, e.g. Jeroboams is created this way with the exception of a couple of small and very eccentric houses.
The bottom line is that champagne in bottles smaller than a full-sized bottle or larger than a magnum is going to be worse than champagne in full-sized bottles. It's been handled more and decanted. At the very least, it's lost a little fizz in the process.