Demagogue

It was my understanding that Duncan Black, aka "Atrios," had a PhD in economics. At least that is what it says on his blog

Atrios is the pseudonym of Duncan Black, a 32 year old recovering economist living in Center City Philadelphia. This blog has been online since April, 2002, and currently gets an average of over 100,000 visits per day.

Anyway, today I was looking at his Blogads and was wondering what it costs to advertise there and found out that it is not cheap

1 week ($1500)
2 weeks ($2500)
1 month ($4000)
3 months ($15000)

Now, I do not have a PhD so I might be completely wrong here, but if you can advertise on Eschaton for one month for $4000, why would you pay $15,000 to advertise there for three months?

If it were me, I'd just advertise there at the monthly rate for three consecutive months and ... you know ... save myself $3,000.

But, like I said, I'm no economist.