T-Mobile has phones as cheap as $150 (admittedly probably not great but still work), and quality phones as low as $400 or $500 for lower end or older iPhone/Pixel models. If you don't know if you can spend $150-$500 for a minor emergency, then you don't have an emergency fund which is easily the #1 priority for personal finances. Same for the Aeron - if you don't know if you can afford a $150 chair, you shouldn't buy it. The amount of the sale is irrelevant by the way - buying something you don't need that is 90% off is still a waste of money.

I don't think you're arguing in good faith. Making a throwaway account just to talk down to other people mourning the loss of their financial planning tool is a pretty shitty thing to do.

I can see how that would be a useful system. My approach/mindset is totally different. Instead I maintain a 1 year emergency fund in my checking account. If something important breaks (e.g. phone), I know I can replace it. Every month or so, I look to make sure I’m not drawing down my account balance. If I am, I mentally calibrate to spend less money on takeout, clothes, etc. If instead my balance is going up, I skim off excess money into an investment account.