Matsuzaka signs?
If SI is to be believed, the Sox and Matsuzaka agreed to a 6 year, $52 million deal, with incentives that could go up to $60 million.

My quick reaction is that this is a pretty good deal for the Sox. When you add in the posting fee, this works out to $17-18.5 million (varying with the incentives). But, the $51 million posting fee isn't subject to the 40% luxury tax. Assuming that the Sox exceed the luxury tax threshold each of the next 6 years (which is admittedly a pretty big assumption), then it's really just around $14-15 million a year. The posting fee is being paid up-front, so to fairly compare this to other free agent deals, the time value of money needs to be taken into account. My very rough calculation is that another $1 million should be added per year.
So, the final result is the approximate equivalent of $15-16 million a year for 6 years. That's right in line with what's being talked about for Zito. Based on everything I've read, I think the odds are Matsuzaka winds up being a better pitcher than Zito. Of course, there's a risk associated with a player who's never played in the majors. Hard to put a dollar figure on that, but I think he'll succeed and that the overall money being spent puts the deal right in line with the way the market is behaving.
Additionally, there's added value to having a premiere Japanese player. I read a Jon Heyman article awhile back that said the Yankees make around $5 million extra a year in marketing/licensing/branding money from the Japanese market. Assuming that's true (I have no idea if it is) and that the Sox can pull off the same thing (some of the $5 mill may be due to Matsui being an every day player and him playing in NYC), then the deal looks very good.