The cost table in that writeup is the part worth doing arithmetic on. It reports the two paths within a rounding error at 500 messages a month, and more than $100 a month apart by 3,000 [8]. Divide the gap by the volume and the managed path costs about 3.3 cents a message more [10]. Hold that delta at the low end and 500 messages would save roughly $16.70 of message cost, which is the amount the author says the fixed lease eats [8], so the long code lease in his model sits near seventeen dollars a month [11]. Parity at 500 is therefore the break-even, and every message above it is that lease being spread thinner [8].
For the shape to transfer to your account, several things have to hold. Every message goes to an Australian mobile number at standard pricing rather than a negotiated rate, and you are comparing a single long code lease [8]. The x-axis is messages, not logins. Resends and failed deliveries are messages, so a forecast built from expected sign-ins puts your crossover later than it will actually arrive.
The service menu is less tangled than the search results make it look. SNS Publish still sends, but since late 2024 its SMS traffic runs through AWS's newer messaging backend [3], so choosing SNS chooses a thinner API over the same delivery engine. Origination identities and configuration sets live in End User Messaging [4]. Notify sits on top of that same service with a shared, pre-approved sender identity and built-in fraud protection, and that shared identity is precisely what buys you out of the registration queue [6]. Your own number is cheaper per message and slower to start, because carrier registration takes real calendar time to clear [7]. There is also a send-and-verify pair where AWS generates and checks the code, billed per successful verification [5]; that is the one line item priced on users who complete a login rather than on attempts.
Then the defect. Creating a Notify configuration in the console returned ACCESS_DENIED_CONTACT_SUPPORT with no stated reason, while the identical configuration created through the CLI went active immediately, and the author says he has no confirmed explanation [9]. The account plainly held authority to create the thing, because it did [13]. The refusal traces to the console's path around the create call, separate from the create action itself. The console is an API client with opinions.
What the writeup does not carry is the rule. It gives the date and says the AWS side changes, without setting out what must be registered or by whom [12]. That schedules the decision but leaves the work unsized.
