The prices don't drop that drastically. Plus if you buy any high end hardware, especially if its the first wave from an architecture that massively boosts performance (first gen i7s, Q6600s, Geforce 8800GT, Geforce 670), they stay relevant for an extremely long time.
Only reason why I scrapped my old computer was because I wanted to go from 1080p to 3440x1440 and VR...and that was 8 years old, still running everything at very high to max settings if it was rendered at 1080p.
Now if you're one of the crazies that are constantly chasing for the best.....well that's not very smart =P