LG determined that the more expensive version wouldn't make financial sense in most places.
Charging more money for a lower specced device doesn't make financial sense in any place, the European LG G6 only comes with 32GB memory and no DAC yet at £650 rrp is almost the same price as the 64GB Galaxy S8 which not only had double the memory and the faster Snapdragon 835 but also the much more attention grabbing AMOLED infinity edge display.
Selling the G6 plus 128GB model for that price would make a lot of sense as the high amount of memory would like grab some attention and makes up for the lower specs in other areas. What's even more crazy is that the grey import 64GB models with the DAC are almost half the price, even allowing it costing a bit more to officially import it the UK pricing makes absolutely no sense and it's no surprise the phone has been a poor seller.
I'm disappointed to hear about another plus mode unique to South Korea as it sounds like they're going to take a similar approach to the G6 in which case I'll be going with Samsung who don't take a screw Europe approach.