I live in a wine growing area and wine is cheap. German supermarkets do sell little bags, like teabags, of a spice mix which you just infuse in the warm wine.
My method, when I'm only making it for the two of us, is to cut up an orange, a lemon, or any other citrus fruit I have to hand, into fairly thin slices, add a stick of cinnamon and a couple of cloves, pour over about half a litre of good red wine and heat it up in the microwave, on a low wattage to give it time to develop the spicy taste and to prevent it boiling.
I then pour it into the glasses the Germans use for tea (double sided if possible, but mine aren't) and stir in a spoonful of honey.
The mulled wine you get at the Christmas markets (when there are any) is no longer as sweet as they used to make it. I can't comment on the ready made bottles as I don't buy them. Last year some new variations appeared - Hugo (with elderflower, I should think) and other types with a white wine base.
It's so easy to make yourself, I don't see the point of buying the made up stuff.