Here’s a cool cross sectional view of a high quality Leica lens, showing just how many glass and metal elements to into creating the finished product. Of note in this view, you can see how much actual structure is required around the glass elements, to make everything function correctly. Cross Section Views of Leica Lenses on Petapixel.
Also regarding Leica, today the 1923 Leica 0-series camera was sold for USD $1,890,000.00 at an auction. Now that’s some expensive glass.