There are no "brand new" iPhone 5 models for sale anymore. The lowest price iPhone is the iPhone SE at $349. You can buy three of those instead of one iPhone X. It's three generations old.
No. Look at Amazon. You can buy all sorts of brand-new iPhone 6’s for well under $300.
I suppose you could convince yourself that a brand new thousand dollar iPhone is well worth the cost over a new $300 iPhone 6. But you are in a very small minority.
Not necessarily true. My wife and I bought new iPhone 5s models at Target last year, operates via TracFone service. I see that they are still advertised for sale at Target Stores now, for $199. I believe you may be able to get an iPhone 6 on TracFone service for $288 at Target online. TracFone is no contract, and the service cards for minutes is cheap. Costs me about $9/month when I buy a 1-yr card. I have about 6,000 minutes saved for data/text/calls from carrying over minutes from previous TracFones over the years.