Why don't you ask somebody who pairs, rather than writing an uninformed rant against it?
> If you are customer, you pay twice as much and you get churn.
Oh I get it, you're approaching and commenting on all of Agile from your software-as-contract-work perspective. Let me enlighten you: most software isn't sponsored by a single customer on a per-diem basis. But while we're here, let me say this: if you truly think you get half the productivity from a pair, then you fundamentally misunderstand the gains of pairing.
> I recommend a more efficient alternative – review pairs. Person A and person B use a code review system to review each other’s code before release. You get the same benefit without the neck cramp and the BS.
There is more to benefit from pairing than just on-the-go reviewing. There is also the fact that you retain your focus much easier, you spread technical knowledge when you shuffle your pairs, etc.
But on the subject of reviews, your reviews are also much better because they benefit from FULL context, and the suggestions and modifications are made EARLIER (which is much less expensive than getting to the point of being ready to commit and having to refactor everything).
Oh and about the neck cramp remark: do you really expect your devs to pair without having mirrored monitors, two keyboards, etc?