No problem if you split the gains 50-50. 2.5x raise for the one person.

Why though? That’s wasteful. If I could run my business more efficiently for the same spend that’s great.

Then you're going to get called a greedy bastard.

Not by me. I know you'll go out of business if you pay employees 2.5x your competition.

It will even turn out ok if the other 4 people find new work that pays the same. But if everyone fires 4 out of 5 employees because they're focused on "run my business more efficiently" to the exclusion of everything else...it's not going to end well for any society.