I just don't understand how that is anything but a net loss to "just go". If you really need/want to leave, then that makes sense. But if you would have been satisfied to stay if the compensation was appropriate, why not have that option? Not only do you have to start over with no rapport with the rest of the office, no seniority, no earned respect, but your current employer is blindsided and almost surely in rough shape because of it.
Now I don't know the OP's situation, but I'm in a small business. I only have a handful of employees and each one requires months of training before they are effective in their roles in our workflow. In the time that they are not effective, I have to pull 80 hour weeks to do their job and mine. Further, it costs me thousands (a real percentage of our yearly revenue) to advertise, interview, hire, and retrain someone else. I don't have the resources or space to have multiple staff for each role, so if someone just quits on me, it's a disaster. Again, maybe not the OP's situation, but I'm surprised how many posts here think their employer is a faceless entity that would fire them in a second. NOT ALL BUSINESSES ARE LIKE THAT.