Over the years tons of things have shrunk in size whilst getting priced higher, nothing new really.
It's not just the shrinking it's the overall decline in quality/taste I find as well.
I remember KitKat's from my youth having a lot firmer bite, and the chocolate taste being a lot stronger. The same with Lion bars, Cadbury chocolate etc everything is a watered down smaller size version now.
It's this constant obsession by companies to chase every last bit of profit they're willing to compromise on the integrity of their own products.