Don't overlook the budget lines. The Google Pixel "A" series and the iPhone SE use the same high-end processors as their expensive siblings but save money on screen tech and materials. You get the speed and camera quality for roughly half the price.
Buying a new phone doesn't have to mean dropping $1,000 upfront. If you’re looking for the absolute cheapest path to an upgrade, here is the hierarchy of savings: cheapest way to buy a phone
Note: If you have a cheap prepaid plan, switching to a major carrier just for a "free" phone usually costs you more in monthly fees over time. Don't overlook the budget lines