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120 degree eyepiece
With the very best coatings possible, an 11-element eyepiece, even with all separate lenses (unlikely), or 22 air-to-glass surfaces, transmission could be as high as 97-98%, so coating technology has already made this possible (think high-end camera lenses).
But the one thing you can't escape is wavefront degradation. Every glass surface has a particular peak-to-valley wavefront accuracy, and the errors could be additive (not likely--there should be some error cancellations), so the surfaces have to be more accurate the larger the number of elements.
That's why eyepieces with high element counts that also happen to be sharp and show little or no light scatter are expensive. It takes a much longer period of time to make them. Add more materials, better coatings and slow production, and it's not too surprising they cost more.
And if the design of the Kohler were improved to the best modern astronomical standards, I shudder to think of the costs!
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