I happen to have had Kontakt as part of Komplete 8 Ultimate - going through many upgrades from 3 up to 8. I stopped at 8, because the newer versions didn't really give me much of anything different than I already have.
I also picked up a handful of 3rd-party instruments, which were not very expensive.
I ALSO hunted around, and found a CRAZY number of FREE sample libraries for Kontakt - nearly 1 TB of sample-based instruments that are really quite good.
The other part of my sample collection comes from a monthly subscription I began with EastWest Composer Cloud, which gives me another IMMENSE number of REALLY good - literally motion picture quality sample-based instruments. This runs me $29 a month, and gives me another full TB of samples and thousands of additional instruments.
Between Kontakt, Play (the name of the EastWest sample player that plays the Composer Cloud instruments), and all of the free samples I found for Kontakt, I have tens of thousands of incredibly good sample-based instruments and sounds.
Rounding things out, I use the Arturia V Collection, which I find incredibly good for all of the vintage synth sounds, and then I picked up the Korg M1 soft synth from their Legacy Collection. The M1 comes with their entire collection of expansion sounds - 17 different packs of them, and includes all of the sounds from the Triton.
So the cost of the above sounds is approximately:
$150 for the Arturia V Collection - if you get it on sale, which seems to happen in December or January
$24.99 for the Korg M1 - on sale - currently not on sale but still only $49.99 which is still incredible
??? Hard to break Kontakt out, since I bought Komplete and upgraded from 3 up to 8, inclusive. Kontakt runs $399 for the full version - and the Kontakt Player is FREE.
$29.99 for the EastWest Composer Cloud - which is a monthly charge that gives me access to an absolutely stunning and amazingly large number of world-class instruments and libraries.
And then I have 160 Kontakt instrument libraries that I found and downloaded from the web, and these are also really quite good.
I hope some of the above helps,
Bob Bone