What currency are you talking in? There's only a $300 premium (at list price) in US dollars for the Studio Display.
I have a 27" LG 5K from the initial release batch. A lot of people consider it ugly, but mine is on a VESA mount. It's just a floating black square on my desk.
If I had to buy it over again would I pay the $300 premium? I haven't given the 27" Studio Display a try yet so I don't know, but if the sound and camera are much better, the price difference seems very reasonable to me, especially if owning the actual Apple branded product might make for a more hassle free experience.
That said, you can easily get discount pricing on the LG so the actual price difference is more like $500.
The LG 5K has always felt like it was 100% compatible, but not 100% supported. There have been all sorts of quirks requiring workaround for some 5K owners to get their displays to work with different setups. You can find their testimonies in the forums here. Granted, it'd be unrealistic to expect that the Studio Displays will be entirely headache free themselves.
My 5K panel has problems with ghosting that's doesn't bother me too much, but would drive some people bananas. Does anyone know if the ghosting issues have been resolved for good in these panels? Some 5K iMacs have been known to suffer from ghosting as well, so again, paying the Apple premium isn't a guarantee of avoiding the issues that have affected some LG 5K owners.
I'm personally hoping for the rumored 27" display with ProMotion to be released. If that comes out and it's not bonkers expensive, I'll be lining up for one early. If that takes forever to come out, I'll be considering a 27" Studio Display within the next 2 years and bump my LG 5K down to a second display.