I've dabbled with the best of the Nikon's 24 1.4G, 50 1.4 and 1.8G, 85 1.8G, 200F2 ( that last one is one very special lens! ). Have yet to play with the new fanciest Sigma Art and or the uber expensive and snobbish at the highest level Zeiss ones, LOL
Now have the 20 2.8D, 24 2.8D, 28 2.8D, 35F2D, and 50 1.4D and soon will own one of the 85 1.4 D lens. I do find them sometimes more fun to shoot both wide open and stopped down. I personally have no need for the cost, sharpness and perfection of them uber expensive as with these primes I don't print larger. They have plenty of faults that I can see when mounted to my D810 but it is all about good enough and fun right? I am having so much fun in fact I see a Df returning to the stable soon! My conclusion after seeing the peepers and measurbators fap, for them may be worthwhile, but for me, find better to drop that crazy amount of money on a body ( my film of yesterday ) gets me far more pleasure and immediate return than those lens, but that is me.
Seriously, I'm the last to not believe the latest isn't better, but at some point good enough is good enough. I still see some measurable gain in the bodies. There is a place for some of the pricier stuff and I do own them 24-70E, 70-200VRII, owned and sold 14-24G. I still lust for more reach and speed; 300 2.8, 400 2.8, 200-400F4 and the Sigma 120-300 2.8 sports, and the Tamron 15-30 2.8, but finding on the prime side for fun and not sport the cheaper older stuff is what I'm more than happy with. Dang they will last well into my retirement, hope Nikon keeps on putting focus motors in the Df2 and D6!