I don't think MDVN is overvalued either. But it is tough to estimate peak sales revenue in PC. Even though it is considered more effective than Zytiga, it is going to share revenue with Zytiga IMO - how much I don't know. I think the key is whether it is effective in Zytiga treated patients, and whether insurances will cover for Zytiga treated patients. If they do, it will broaden patient population for Ztandi.
The other fact to consider is Zytiga loses US patent protection in Feb 2014, NCE exclusivity in Apr 2016. It is difficult to say what effect it will have on Ztandi.