You can easily get SEO hosting with different Class C IPs and mix in a few other hosting services for less.
Also, why not mix in a few free platforms like 20 High Quality Web 2.0s?
Web2.0's can easily get banned anytime so I don't really think it's a good idea to use them.
As of my experience for domain that is PA/DA >30, PR >2 and Age >1 you need around 10$-30$ I wouldn't spend more then that on domain and with this price I could easily get few PR5 and PR4 domains too.
About the hosting, c-class IP hosting shouldn't cost you more then 1$ per domain so yeah the cost is around 45$ per year per blog in private network.
But the main thing is, let's say you built a network of 25 blogs that is 1125$ per year, you can keep posting links to those blogs until OBL reaches like 30 or so, so that is 30*25=750 posts, now look at the bst section, on average cost of a post in private blog network is 12$ I think so for 750 post you'd get 9000$, content can be generated or you could go with cheap writers who write posts for 2.5$ or something.
But, the better would be to use this network for your sites, you now got ability to create 25 top-notch quality backlink for your 30 sites, so why not rank them and earn money from your sites? you can post 750 high pr, high da, permanent links for 1125$ you can't ask for more
I mean that you shouldn't consider private blog network is built for one particular website only, you build it for bunch of your websites, and well, if you don't make 1125$ back from 30 ranked websites then IM definately isn't the thing you should be doing for life
