My SCOBY has grown so all I need to double my output is a second glass gallon jug (coming in the mail), five more bottles to decant into (got ’em) and space in my fermenting area (not a problem).
For one cup of sugar and four tea bags, I get about $20 worth of live-culture kombucha. Most commercial brands of kombucha are pasteurized, which kills the probiotics. They taste the same, but aren’t as good for you. GT’s brand is live-culture. Look for it in the cooler section. You may need to be of age to buy it, because it’s got a small amount of alcohol in it.