What is the normal price of 400 PR4 or higher links (10 PR5, 3 PR6, and 2 PR7) What could you see yourself spending monthly? The links are spread across 5-7 different domains.
You can look around link adage and other auction/brokerage sites to get a better idea of what people are selling for, but from what i've seen, for 400 PR4 on a few domain, you'd probably be looking at $50-100 depending on if it were themed or not.