Earlier quoted context omitted.
> Twitter said that's why they got rid of the SMS 2FA. They said it was costing millions to have that enabled for them. Previous Twitter employees have said that this is incorrect. Because Twitter began as an SMS-only (and then SMS-first) application (remember 40404?), they very early on established direct-connection infrastructure for sending SMS, meaning that they have a marginal cost of literally $0.00/message in…
> they very early on established direct-connection infrastructure for sending SMS, meaning that they have a marginal cost of literally $0.00/message in most markets. I am very, very interested to understand how that works, because without more detail or sources I'm calling bullshit. I definitely understand how Twitter could have greatly reduced their per-message fee with telecom providers, but at the end of the day T…
For something like Twitter where you could post by SMS, the balance of traffic might have been such that giving Twitter free outbound SMS was balanced by the charges incurred by customers sending to Twitter's shortcode. Or it might just be balanced by increased customer happiness when they can use the product more effectively.
If the carrier doesn't run their own messaging infra, they might be paying their IT provider on a per message basis, and might not be able or willing to set the messaging rate to zero.
For a use case where SMS is used to show control of a phone number, getting a zero cost direct route is a harder sell, but it can happen if the routing through aggregators is poor and the carrier is concerned about that, or if there's some other larger agreement in play.