Too expensive at $120m unit cost. The market is willing to pay $70-80m.
More important for the Europeans to make up their minds on 6th gen unless they want to end up losing the capability alltogether and irreversibly.
Just revisit 1980s Boeing studies like the 7-7 and the 7J7.
Dreaded auto-correction. :)
Without a thrust increase, for take-off the -10 will have to solely rely on the curvature of earth.