The question is not whether they can find someone else to hire. They can always do that for the prevailing market price. The question is, how much more do they have to pay to get someone to take on ~$30,000/year in commuting costs than they would if they didn't require that?
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?
