Something tells me he wouldn't be having such a dilemma when he needs to spend $1000 or more in two years for a new flagship cell phone.
Nevermind how much less a new camera costs and how much longer it will be useful for.
And while my 12-year-old full-frame Nikon D700 might only fetch a token sum now, it'll still take photos that are on a different level from any camera phone out there.
Thousand-dollar phones are a sunk cost, and it's common to only recover between half to two-thirds of the cost after one release cycle.
Moreover, $1000 will get you a flagship phone, but at best a mid-level camera and lens. You'll get a vastly better camera, no doubts, but you'll only get a camera.