I bought a used pair a few months ago for a little more than what I would find a new one for (around 140-150). I also bought two desk stands and set them up at the exact height I wanted. Initially, they have the iconic look with the yellow and black cones, they are beautiful and the white gives them a different character.
Now, onto the important things, I haven't used them for heavy music production, but for the little I needed them, they are definitely okay. They have a somewhat colored sound (they are a bit bass-heavy for my liking, but with the EQ and various settings, it balances out). They connect easily and seamlessly with my cheap sound card and didn't require any drivers.
If there's something that bothers me a little, it's the volume, at least for music. When I have the output of the sound card at 50%, the volume of the computer at 100%, and no adjustments in the speaker EQ (either for bass-treble or output, all +0dB), then the volume is just satisfactory for personal use, plus. Up to 60-75% on the card is a normal volume and my limits for personal use, but beyond that (almost suddenly) they go crazy loud. Although I expected them to have an even higher ceiling, meaning they could be louder without me having to push them.
Maybe it's because of my 80€ sound card, maybe the cables the guy gave me that I never changed, maybe the stands, maybe the acoustics of the room. It doesn't really bother me though, for my standards, they are exactly what I need, and I imagine the same goes for the average hobbyist.
I definitely haven't fully utilized their capabilities, nor am I an expert. So, I can't judge the quality-price ratio with certainty. I don't know if I would buy them new for that price anyway - I didn't have and still don't have the budget. For speakers that cost 250€ together, they didn't impress me that much. For the money I spent, they are definitely fine. However, I haven't compared them to many other models yet, so I don't have a benchmark - after all, I come from simple Logitech 2.1 speakers.
I should also mention that the KRK logo is illuminated, which is a nice touch/detail. During the day, it doesn't stand out much, but in the dark, it glows quite nicely. With regards to the light, it reminded me that if the speakers don't receive any signal for half an hour continuously, they automatically turn off - something I appreciate because I don't like constantly turning them on and off from the switch at the back. (As soon as you play something again and they detect any sound, the speakers automatically turn on without much delay, as if they were never turned off. So even if you forget to turn them off a few times, nothing will happen.) The light also turns on and off automatically, so it indicates whether the speakers are on or not.
I will come back if I reach a different conclusion or if anything changes.