The LS50s (recently manufactured examples) can compete with many ~$5K speakers IME. However, getting them to do that requires a high quality amp and source. If you pair them with a budget amp, say something in the <$1k range, as one likely would with $1500 speakers, you won’t realize their full potential, especially concerning their bass. This is why some find budget speakers like the Elacs to be nearly as good. It’s because they have system bottlenecks elsewhere.
It’s better to think of the passive LS50s as a $3500 speakers, because they simply require high quality gear. I run a pair with a budget amp in a third system. They sound ok for that application, but having had them paired with $2.5K amps in my other rooms, I know they’re capable of far greater performance. I wouldn’t read too much into comparisons with lower KEF models. Stereophile recently rated the Q350s as "class C" speakers while the LS50s remain "class A." I’ve owned and auditioned a fair number of their class C rated soeakers. The LS50s are in a whole different ballpark when properly powered. The wireless version is a better value proposition unless you already own a high performance amp.