Pricing goods in different containers

[Grim Portent]

So a thought has come to me, a bottle of good wine in the PHB costs 10gp, a bottle(glass) costs 2gp and holds 1.5 pints of liquid.

What if the wine was purchased in a barrel instead? A barrel holds 40 gallons and costs 2gp. Assuming my math is correct and I'm not being stupid, that's 213.3 bottles worth of volume.

So the question I have is, is the cost of the bottle included in the cost of a bottle of wine? If it is, is it full price or half price?

Basically does a barrel of fine wine cost 2133 gp, at 213.3x10, or does it cost 213.3x8 for the unbottled wine, plus 2 gp for the barrel coming to a total of 1706.4 gp?

[JellyPooga]

Ah, my friend, don't think so hard! For you we do special price. 2000gp per barrel is good discount, no? It's not my best stock, of course, but is good price. How about this, if you pay in platinum I'll give it to you for 190.

You want something a little cheaper? Not to worries my friend; this barrel over here is practically vinegar, but you water it down and the yokels won't tell the difference. 1500gp and it's yours, or you can buy two for 250 platinum. My best offer.

Oooh, you want to know about the good stuff? Ah well, the best doesn't come in barrels of course and the glassware doesn't come cheap...This here is a 405 vintage, a good year and a good price at 20 crowns a bottle, but if it's only the very best you want, it doesn't hold a candle to the Summerwine of Eldari. Even the cheapest bottle of that will set you back 50 platinum a bottle. Imperial stamp only, I'm afraid and I'll need to see your papers before I'm allowed to sell it to you. Tax man takes his cut, which means more paperwork for my accountants. The cost of the high life my friend...