You might be intrigued to know that all of these are uniquely American ideas. The US might be the only country in the world where those "Rules" are assumed: for example, most countries don't have "ask your doctor about ..." adverts.

I'm in the UK and got married over two decades ago. Looking now in decent high street jewellers (i.e. not the cheapest, poor quality shops), the average price for a traditional diamond solitaire engagement ring is about £1,500 with most coming well below that. The average person in the UK earns £689 per week, so that's closer to two weeks than two months.

Sure, wedding costs here might on average be comparable to over there, but almost all my friends spent half that and had pretty ordinary weddings, so (like the salary) I'm guessing there's some upward skewing of the stats by the big spenders.

If you just say to the vendor, "What can you do for half that price?", they can be surprisingly inventive.

Like you say about adverts, it's about questioning the assumptions: the rules might not be rules at all.