Materials, general quality, strength to noise ratio, charging mechanisms, packaging, lifespan and warranty.

In my experience, most cases when luxury toy gets bad reviews it is because it doesn't work for a particular user do to basic preference differences (they prefer super strong vibrations but purchased a medium strength luxury vibe, complain that it's weak) or anatomy problems with the shape of the toy (see the Lelo Ina). Although those certainly warrant strong consideration in reviews, I personally do not consider a negative review for anatomy differences the same as negative reviews that says "this crap broke after a week and there's no warranty" or "the material began to stink and disintegrate after four months." One is a matter of personal preference and how well it worked for a particular user, the other is a matter of working in general and not.

Edit- here is a quote from the founder of luxury brand Jimmyjane that basically speaks to this:

"For Jimmyjane this means we extend our attention to detail across every component - the materials (all medical grade), product, packaging, manual, marketing, customer service, and even an unparalleled 3 year warranty. We’re fundamentally reimagining a category of product that people assume to be cheap and taudry - so it’s that much more important for us to attend to every detail, and demonstrate how different the experience can be."

So really, luxury toys are luxury for all the same reason certain clothing items, cosmetic products, tech gadgets etc are considered luxury. If none of that is something you care about, then yeah, it'll just come down to price.

I agree with Cherrylane's list.

I also agree that a negative review due to preferences isn't quite the same as a negative review over quality. I've written negative reviews on luxury items that didn't work for me because of preferences, but could still have worked for someone else. I usually mention in the review "didn't work for me because of XYZ, but might work for you if you like XYZ." That way it's different than just saying "this thing blows!!"

The only luxury item I have ever had a real issue with was Form 2 and The Glitch. I love that thing, but man if it's not ever annoying. Almost all of them do it, so you could make a claim on it but still possibly have the same problem. So I just never bothered.

Mostly, with a luxury item you know you're at least getting something high quality. Now, if it will work for you is as much of a chance as it is with any other toy. A high quality material, long lifespan, rechargeable battery, etc. won't promise that the toy will do anything for you.