Absolutely, there are hidden costs, in both directions.

If you only hire within the pool of people who are willing and able to commute to your office, you'll both need to pay more and have less choice. Workers are more tired as they spend hours commuting every day.

On the other hand, it's harder to develop juniors if all your seniors are working from home. Written communication lacks context that helps difficult conversations move forward. Silos build up as people in different teams never see each other.

In the long-term, I believe the broader benefits to society and the planet mean fully remote working will become almost universal. In the meantime, a hybrid model of mostly remote with broadly-attended meetups is the best combination. But some companies will decide that everybody being in the office all the time is right for them, and they can perhaps leverage some benefits of doing so.

I didn't personally calculate it, or see exactly how they came to it. But I know it included things that all employees need, whether remote or not, plus a few things specifically needed by remote employees. For example:

* Laptop

* Accounts like email, Slack

* Entertainment (e.g. Christmas party)

* HR (this covered specific HR services like payroll, not the whole thing)

* IT support

* Travel expenses

* Home working budget

* Training

They did say it includes taxes, maybe they are including a 3% pension contribution or even Employers' NI which can run to 12% of salary.