So suppose the employer's benefit from having the employee is $150,000 if they work from the office and $140,000 if they work from home. Meanwhile the employee would accept $130,000 if they had to work from the office or $100,000 if they can work from home.

You're saying, $150,000 is more than $130,000 so the employer can pay them $130,000 to work from the office and everything's fine.

But the difference between $150,000 and $130,000 is less than the difference between $140,000 and $100,000. By quite a lot. So why isn't the employer going to want any of that money?