No way it's more expensive than paying rent for an office in a trendy city and commuting to said office.

That's not what I was implying. I noted the Buffer retreat since that's a hidden cost of remote work I haven't seen people discuss.

It's a completely optional cost, though, not a hidden cost. Plus it sounds like they allowed everyone to bring their partners and families, too. And, most companies that have physical offices also have corporate retreats or events, so it's not even really exclusive to companies that work remotely.

> most companies that have physical offices also have corporate retreats or events

Citation needed. I'd never even heard of a corporate retreat before now.

Valve flies out the entire company with families on vacation once a year.

Actually, if you look at the data they published they show that the retreat was much more expensive than their rent.

    Retreat: 5.2%
    Office:  2.1%

But they were never renting office space for their entire staff. If you really wanted to compare apples to apples (i.e., "Should everyone have an office payed for by the company" or "Should we have an annual retreat for the whole company"), a bit more analysis is needed.

Breaking down costs like that (per end user payment) is awesome; I'd never thought of doing that. (It's not very accurate in a lot of businesses, but it's an interesting way to think about things, so it's a useful tool.)