I was in my local Natural Food store this week picking up some supplies and they have 5 gal water bottles there for $18. Glass carboys filled with spring water!!
They also have 2.5 gal glass carboys filled with spring water!
I think they were around $12.
I have never seen 2.5 gallon carboys before. These were the same diameter as the 5 gallon ones, just short and fat.