There are, I think, three reasons to have a blog:

1. to demonstrate your expertise
2. to get some Google juice
3. to have a website and online presence that feels dynamic.

They are all valid but without the demonstration of expertise the other two become a bit pointless.

Alan Vitberg argues that the cost of creating content in-house can be zero - which from some angles is true. But my experience of talking to Partners is that they are totally focused on the Opportunity Cost. And that for a partner is say $500 per hour X 4 hours for a good blog post: $2000.

That is a big number that gets very big indeed if you need to post daily or weekly.