We know how much the Concorde cost to operate: a zillion shittons (metric) [http://www.concordesst.com/retire/faq_r.html http://www.concordesst.com/retire/faq_r

We know how much the Concorde cost to operate: a zillion shittons (metric) [http://www.concordesst.com/retire/faq_r.html http://www.concordesst.com/retire/faq_r.html] . And that was with proven technology and all the sunk costs behind them. I think that makes a sensible floor for this project, unless you are willing to argue that researching and deploying this completely new technology would somehow cost less.