Cocoa powder and milk powder (or more rarely condensed milk) are expensive and contribute to taste and / or texture.
To make cheaper chocolate you increase sugar to save on cocoa (there's a hard lower limit of cocoa content however in many countries and the EU) and milk.
Vegan milk-like chocolate also has lower protein contents, but in my opinion it's a different product where this rule of thumb does not apply.
OK, what percentage cocoa solids and milk solids do you think Toblerone should have? Because they're already at 28% and 14% respectively. Which seems like plenty, they're not skimping.
For comparison, for example, Cailler is 28% and 20% respectively, which is a little bit more milk but that's all. [1]
Toblerone doesn't seem like "cheap chocolate". It's just slightly less milky than another premium brand, and has other ingredients like almonds and honey.
Toblerone has 62% of sugar, I'd personally consider anything beyond 55% of sugar as cheap chocolate. Also 28% of cocoa is definitely on the lower end, I expect quality chocolate to be at 30% of cocoa.
I agree that Toblerone is candy. This also explains why it's hard to find good Swiss or Belgian (e.g. Leonidas) chocolate that matches the 62% sugar content of Toblerone.
To make cheaper chocolate you increase sugar to save on cocoa (there's a hard lower limit of cocoa content however in many countries and the EU) and milk.
Vegan milk-like chocolate also has lower protein contents, but in my opinion it's a different product where this rule of thumb does not apply.