Re: Hold up a sec... (et al)
Regarding the price differental between fifths/magnumsJeroboams/Methuselahs (not to mention Rehoboams, Salmanazars, Balthazars, and Nebuchadnezzars) of cahmpagne:
having worked in the liquor biz (retail) I think that I can answer this. In general the latger sizes of champagnes cost significantly more than a simple multiple of the 750 ml size due to several factors, most of them having to do with the fact that they are sparkling wines.
Note, for starters that the bottles must be significantly trhicker than the standard, since the wine is under pressure. Simply making the bottle larger while keeping the walls the same trhickness would, essentially, produce a wine-grenade with glass shrapnel. Not a good thing.
Now, increasing the size of the bottle linearly squares the surface area and cubes the volume of glass used. But because of the additional pressure the bottle-makers use significantly more material per bottle than the simple mulriple/square/cube law would imply,
Secondly, having already used x times as much champagne (a commodity of limited production) and increased the price that way, then adding in the increased price for the materials in the larger bottle, you have a niche product designed mainly for displays of wretched excess. This limits the number sold and, hence, the number of bottles that the champagne-bottllers purchase from the bottle-producers, again raising the price of each bottle (smaller production run + more material used = greater per-unit price).
(This, by the way, is probably why the party in question was forced to limit themselves to the relatively mundane Jeroboams and Methuselahs. The larger Salmanazars, Balthazars, and Nebuchadnezzars - 9, 12, and 15 L, respectively - are, IIRC pretty much special orders, produced on demand and not normally kept in stock in even the most upscale of wine-bars.)
Thirdly, because the larger sizes are generally sold BECAUSE they are intended as brilliantly impressive displays of excess and BECAUSE they are scarce commodities, the wine producer is safe in charging a premium on TOP of the added production costs, which (in the states, at least) is then COMPOUNDED as the importer, wholesaler, and retailer all add in their markups.
Lastly, as a general rule (again, here in the states - or at least in the ones where I've worked in the biz) bars/restaurants are required to price ALL alcoholic beverages on a PER DRINK basis. Thus any FULL BOTTLE sold must be calculated as "$Bottle == price per standard portion x number of portions/bottle". Now this is the only part of the whole price calculation which is a straight multiple but, again, you're making this calculation AFTER all of the markups have been compounded...
And there you have it: more than you probably ever wanted to know about champagne pricing.
(Does using "$Bottle" in the calculation give enough of a programming flavor to get past the "Where's the IT angle" whiners?)