Archimedes - No, it's not just you. I think the 'cheaper
American alternative' referred to is the F-35C (vs. B), not the F135 (vs. F136). According to the HASC, the acquisition cost of the F135-PW-600 (F-35B) has risen 47% in the last three years, outstripping the -100/-400. Much of the increase has been due to the recent hike in metals costs, but the premium charged for the F-35B has nevertheless continued to grow.
Anyway, since Rolls only has a 40% stake in the F136, I think it'd be a bit rich calling it 'Rolls Royce's engine.'
I/C