I think it would be more expensive to self-publish because a large publisher has access to economies of scale. To press, package and distribute one game could become quite expensive for an individual or small group because they'd have to invest in the equipment or make the basis of one product. Big publishers have the production equipment (for say, colour printed boxes) already available and they can spread the cost of this over the wide variety of games they put out. Also they already have distribution channels set up so they can easily get games to market without having to get into individual negotiations with each different outlet.
It's a nice thought and it would quite likely lead to some good games (without the commercial pressure from publishers). Sadly, I just don't think the financial side of the equation makes it as practical as we'd like.
