The flipside is that that 5-year amortization continues even if you did fire everyone, right? Because the costs already happened. So if we consider forward from year 5 of your example, with everyone being fired at year 5:

Old:

Year 6: 1000K profit

Year 7: 1000K profit

Year 8: 1000K profit

Year 9: 1000K profit

Year 10: 1000K profit

New:

Year 6: 200K profit (End of year 1 amortization)

Year 7: 400K profit (End of year 2 amortization)

Year 8: 600K profit (End of year 3 amortization)

Year 9: 800K profit (End of year 4 amortization)

Year 10: 1000K profit (End of year 5 amortization)

Of course this "wind-down" period is unhelpful if you're actually shuttering the business...