It's a subjective thing.
I have bought libraries just for 2 or three sounds that I like in it.
For me it's a matter of time vs money.
If you've got time you can build your own library with your signature and unique sound, but if you haven't and you equate the time required vs the cost of some of these libraries, these sound economical enough.
Note that this is a niche market, There are only so many Kronos Users.
If you account in for the man hours and equipment the makers of some of the libraries have put in, they all add to the production cost.
They do need a decent number of sales to even out the ROI and get into profit.
A lot gets taken for granted, what if these libraries:
1: were not available at all?
2: Came preinstalled, Added to the Cost for each user (who won't even need em)
3: Or Came as Optional upgrades, but only one time option at the time of Kronos Purchase like apple does with some of their macs, you live with what you chose.
in my view what Korg does now is better than any of the three above.
On PC side there is only so much you can do before you hit the bottlenecks.
Kontakt takes it's time to load the patches too and so does omnisphere, if you add some softsynths to the equation and you are not gonna be able to keep latency low enough for long, add some decent convolution reverbs that need sample buckets of their own and you can end up with a lot worse, or much better with lot of spending on processing power and DSP cards etc.
There is no one size fits all. In the end each one of us have to find just the fine balance we can get away with. Where to use computer/plugin and where to use a workstation or other dedicated hardware, only then the true worth of each entity can be realized.

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