"Cost-Effectiveness of Tolvaptan in Autosomal Dominant Polycystic Kidney Disease" 
Annals Sept 17
http://annals.org/article.aspx?articleid=1738493
"Conclusion: Assuming that the benefits of tolvaptan persist in the longer term, the drug may slow progression to ESRD and reduce mortality rates. However, barring an approximately 95% reduction in price, cost-effectiveness does not compare favorably with many other commonly accepted medical interventions."