Originally Posted by Stelmica
What do they have in a wine kit, that I can't get on my own at my local wine supply store?
To make a Merlot or something close.
Most wine kits have a bag that is a combination of juice and concentrate that is pre-balanced for acid and ph and such. Along with sulfites and clearing agents, they will also contain a yeast and usually a type of oak that's considered right for the wine you're making.
The main thing is you can get concentrate, usually a pretty generic one, but you can't get the juice/concentrate combo anywhere else.