It has driven me nuts since childhood, because it's an insult to reason. I'm currently living in the UK, so I'll use £ in the examples:

"iPhone for only £50 a month" "Bicycle for only £30 a month" etc.

What is this, Hardware as a Service? Are you, as the customer, renting the thing or are you buying it? If you're buying on installments (= credit), why doesn't it mention how many months you're going to have to pay it for? £30 a month for a year is not the same as £30 a month for the rest of your life.

Sure, inflation means your payments decrease over time in real terms (and they decrease even more in BTC terms if you're on that standard already), but still, to be able to economize you need that information, so you can apply the relevant discount rate in relation to your opportunity cost over the relevant period. Knowing solely the monthly payment tells you nothing about the price you're paying for the item you're buying. This kind of advertising promotes the impulsive, thoughtless purchasing of liabilities (credit). Or in other words: a slave mindset. It sends the message: there is no future.

Then people end up with dozens of loans and subscriptions that eat up most of their paycheck and they find themselves unable to pay their rent, let alone save.

In the meantime, I'm using a Google Pixel I bought used off eBay for £80 and am on a £4.90 monthly plan featuring unlimited calls, texts and 5 GB of data. But those scummy advertisers would have you believe a "£50 a month" phone is a better deal, because it's only £50 and not £80, and the fact you're going to have to pay another £50 next month and the month after and so on, doesn't matter, because who cares about the future? Only those Austrian-minded, low time preference, right wing extremists.