Right now all model 3s are essentially built the same. The SR only has one motor, and the Performance has tighter suspension and bigger brakes, but otherwise all the cars are essentially the same with various features turned on/off via software.
But lets say they made a more luxurious one. Little nicer seats, better noise isolation, nicer carpet, nicer wood on the dash, perhaps some extra features like a heated steering wheel and a hud. Would you pay more for such a car?
My maxed out BMW 340i xdrive cost about $5k more than my Model 3 Performance. The Model 3 drives better in every way. It's faster, it corners better, and I love never having to go to the gas station and the OTA updates. But I miss some of the luxury. The quiet cabin, the heated steering wheel, the heads up display, Sirius/XM radio, better bolstered seats, etc... I'd be willing to pay $5-$10k more to get the luxury of the BMW combined with the driving dynamics of the Model 3 Performance.
Some might say.... just get an S P100D. I considered it. But then I drove one. It drives like a boat. It's faster in a strait line, but the suspension felt soft and the car just felt big and heavy. Like a BMW 5 series, or maybe even a 7 series. I didn’t like it. I like the smaller sportier size and handling of the 3, I just miss some of the luxury that I had with my BMW and I'd be willing to pay a bit more for a 3 that had more of that same luxury.