Yes. Sizeable CP discounts always.
There are good answers on the $2500 and under question. It would be easiest if everyone could just pop into the store for a few moments and we could explore together in person.
As this is somewhat impractical, I'll take a stab at describing the limitations. First, if you are using the instrument through headphones predominantly, then the sophistication of the sound system isn't that important. Normal piano practice doesn't involve headphones so the quality of the sound system in a digital piano can make a significant difference in terms of authenticity and a more "acoustic"-sounding experience. The two best digital pianos I have, and have ever heard in the 25-years I've been doing this, both have extraordinarily sophisticated sound systems. They create a startlingly "real" piano experience when you're seated in front of them. In most cases, sound systems are the first things sacrificed to get to smaller form factors and lower price points.
Second issue is the quality and performance of the core piano engine both for sound and for feel. Think of sound as the engine and touch as the drive-train / transmission. Both need to be working well, both separately and together, in order to get good performance. I know that the major manufacturer we work with can't put their highest performing action (key mechanism) into instruments under $2500.00. You can get acceptable beginner to mid-intermediate performance out of the "entry" actions, but can't do developmental piano much beyond that level whereas the top-flight actions have a few years of additional developmental head-room. The highest performing digital pianos are now knocking at the door of performance caliber which, considering that a new performance level acoustic upright piano is at or beyond $10000 is pretty good company for instruments in the $4-6000 range.
Beyond the feel, however, is the sophistication and realism of the piano engine in terms of sound. The piano is actually a ridiculously difficult instrument to simulate. There's all kinds of overtones, sympathetic resonances of one string to another, changes over time based on sustain, changes in tonality based on volume and much more besides. The top manufacturers have been on an over 30-year development journey to solve some of these challenges. In the top-flight instruments, we're getting awfully close. The entry-level instruments? Not so much. Are they vaguely piano-like and sort of work and sound like a piano? Sure...but the inaccuracies, errors and oversights will impact how much "true" piano work you can accomplish.
I think, sometimes, of a car analogy as we are all comfortable with the idea that different levels of performance and quality exist in cars. The one difference between cars, or driving, and piano is that the goal is to become a much better "driver" of the piano over time. A "less-than" instrument impedes that process and may, ultimately, preclude the ability to drive much better than at a utilitarian level. Does that mean everyone needs to buy an F1 piano just to start out? Of course not. It does mean, though, that the needs for a piano may change over time and, ultimately, more costly instruments provide more performance. With a certain understandable bias, our industry has always advocated buying the best piano possible to provide that developmental head-room and also to reward even novice playing with a better touch and tone context.
Ultimately, whether it's on the acoustic side or the digital side, the trick is to look at the level of performance that either is currently required or will be required in the future and, as the cliche says, begin with the end in mind. A huge part of my daily job is to take clients through the journey of how piano performance is defined and what changes at the various different price points. We've encapsulated it into a presentation we sometimes do as a workshop called The Art of Selecting a Piano. In that framework, we point to some of the limitations of the value end of the equation.