Most interchangeable lens SLRs and Mirrorless digital cameras today have excellent image quality.
Higher price gets you things like better build quality, weather-resistance, better ergonomics, more sophisticated autofocus, higher frame rates. For some people, those features are worth the money. For others they're not.
Here's a personal example:
Many of you know that about a year ago, I sold all of my Canon fullframe gear and bought an Olympus Pen-F, a micro four thirds camera.
The Pen-F is a medium priced camera in the world of m4/3, costing about $1000 for the body. A couple weeks ago, I bought a new Olympus OM-D E-M1 Mark II. That's Olympus's top of the line "Pro" model, and it cost $1700.
Both cameras have a 20mp Micro Four Thirds sensor. Both have IBIS. They use the same lenses. Same viewscreen. Image quality nearly identical. So, what did an extra $700 get me?
The big thing for me was weather-sealing. I like to shoot in the rain and in other bad weather, and was afraid to take the non-sealed Pen-F out in the rain. I have taken the OM-D E-M1 mk II out in heavy rain already, using the weather-sealed Olympus pro lenses I have and it worked flawlessly.
The pro camera also offers faster framing rates and is supposed to have better AF with moving subjects. None of that matters for me, I don't shoot sports or wildlife, but it would make a difference for those who do.
The E-M1 mk II also has the best built-in grip of ANY camera I have ever used. It fits my small hands perfectly. The Pen-F has no handgrip and I found it hard to hold. I bought an add-on grip for it, which helped a lot but the Pen-F shutter release is on top of the body, not on the grip, so less ergonomic than the E-M1 mk II which has the button on the handgrip.
The E-M1 mk II has longer-lasting batteries and dual SD card slots, too, which is convenient.
So...the high priced camera does not offer better image quality, but DOES offer features that the cheaper model does not. Whether those features are worth the money is up to you, and depends on what kind of photography you do. For me, weather sealing is worth the money because I'll use it. I like the better ergonomics of the E-M1 mk II over the Pen-F, too.