Yeah, that'd be nice if people could take on debt and adjust cash flows like a business, but a lot of people don't have the financial flexibility to spend $600 in a lump payment. That's why people keep bringing up 60+ percent of Americans live paycheck to paycheck. I'm fortunate enough to be able to make those types of purchases a couple times a year, but I know my privilege is not the norm.

The best someone may be able to do is 12mo financing on a new credit card with 0% apr, but miss a payment and its 25% interest. If they even get approved.

Again most people can't afford the up front cost.

Its expensive to be poor, and most people are poor

They are already in debt paying huge amount of interest monthly.

I like being able to charge at home and it's a luxury I know not everyone gets.

For the numbers:

Paying off a $600 charge at $10/month like you suggested would take almost 13 years and cost over $900 in interest at a 18% apr

So you are spending almost 50% more on interest than the original charge. So 150% more expensive at 1500 vs 600.

For a 5 year payoff you have to spend just over $15/month but still are paying over $300 in interest. That's now over $900 total or 50% more expensive because you can't afford the up front cost.