I only zap a post that I feel is under appreciated. A post with 2k sats or more feels like its already well on its way to being on the front page so I don't feel like I need to zap it.

Value-for-value is just a meme unless it is enforced somehow. Zapping is just my way of making sure others get the same value I got.

Maybe one day it takes 20k sats to make it on the front page. In the early days of SN a 200 sat post was front-page material.