also, the weight vs outside sound isolation ratio varies with price.
those are all observable and measurable things.
speakers, they also vary on those audible frequencies, but after you are past $150 per speaker you are only dealing with quality after very loud volumes.
over $3000 for a home system? just be honest with yourself and confess you are buying the prettiest furniture that match your decor.
Last time I looked for speakers in the 400$ (each) range , I could still say that some combo was more clear in the mid range or the highs. It's all about what music you use to test it, some recording (great voices mostly) have very very clear mids which you can tell the difference between a set, the best really open up. Others have detail in the highs that are a lot harder to hear on speakers that are weak there. I don't know past what point you cannot tell the difference, but I do know it's not 150$.
The alternative is to use public announcement (PA) speakers. Virtually all of them are equipped with CDs, but they are relatively large, and unless you have a dedicated listening/home theater room, they won't really fit a home's decor well.
They sound great. Sometimes too great.
This is simply not true, and you could determine that for yourself easily if you wanted to. There are many, many factors that affect how a loudspeaker sounds besides how loudly it's playing. $150 speakers are much better today than they were say 30 or 40 years ago, but they're still full of design compromises.