I would like to know that too, especially given that the battery is smaller. In addition to the glass and wireless charging coil, the overall dimensions of the 8 Plus are ever-so-slightly larger than the 7 Plus, but the 14 gram difference is still surprising.

Remember the glass-backed Galaxy S6 Edge Plus? It somehow weighed 153 grams despite having a glass back, wireless charging, and a 5.7” screen (of course its dimensions were a bit smaller).