A possible option that might fit your requirements is the Chedech Folder out of Korea. They have one version with a similar Brompton style rack for rolling while folded, 5 speed internal gear hub & 18 inch wheels for $2650. u.s. & their ultralight version that weighs 15 lbs or so for $3700. Tried to make sense of the various versions but their site is a nightmare to navigate.
http://chedech.com/shopping-mall-3