Here’s a post on making your own sour cream. All it takes is cream and buttermilk.
I suspect homemade sour cream tastes awesome, but I’m not sure making it will save you any money–unless, as the post suggest, you have made butter and have buttermilk left over.
Or, you can always make your own buttermilk and then use that to make your own sour cream.
Maybe I need to buy a cow…