The jewelers' actions are neither right nor wrong.
Debt in itself is not wrong if it is not excessive and used rightly. If a couple can buy a ring make payments of $150.00 per month yet still save $1500.00 per month, the payment is affordable and the ring can be paid off early, resulting in a decrease in interest payments.
The truth is men do these things primarily to please their wives such that sometimes non-affordability is trumped by wives' anticipated displeasure. When a man views the trade-off in such a light, he buys the ring then begins praying for promotion at work, new sources of income, or some economic windfall.
My ex wife used to remind me of all that was not perfect on our wedding day. It is to avoid such reminders that men buy the rings when they are unaffordable.