What should a socialist economy look like? I'm somewhat in agreement with Marx: we should not be "writing [recipes] (Comtist ones?) for the cook-shops of the future."1 Indeed, to a certain extent, I'm completely in agreement. The point is not to design a socialist economy at all; what the economy looks like, even in its broad character, is not the main point. The main point is to establish the "dictatorship of the proletariat": a society of the workers, by the workers, and for the workers. Economic issues are a means to that end; they should be evaluated by how they move society towards or away from the dictatorship of the proletariat. Because the dictatorship of the proletariat is so far away from my experience, it is difficult to imagine how the proletariat, given real power, will choose to organize their economic life. But difficult is not the same as impossible.
A number of people have discussed ideas for how a socialist economy might work. Chris Dillow describes "his" socialism, directing us to Seth Ackerman's sketch of "market socialism" by way of Matthijs Krul's response. I agree with Krul that Ackerman does not locate the fundamental issue of socialism as located in the relations of production, rather than distribution. Although Krul catches that that Ackerman yada yadas over all the good parts, I don't think Krul really nails down the specific problems with Ackerman's ideas.
Krul hints at the contradiction of the idea of prices without profits, but his objection is mostly Marxobabble. In order to analyze Ackerman's proposal, and why they will fail, we'll need to delve deeply into the nature of "prices" and "markets". Buckle in and hang on to your hat: it's going to be a bumpy and extremely wonky ride.
1"Preface to the Second German Edition", Capital vol. I