TC pricing info: "Paid levels providing unlimited messaging are available for $10, $50, and $150 per month, with access to 1,000 contacts, 100,000 contacts, or 250,000 contacts, respectively."

This sounds like a gamble that the user will buy the service, but never reach the number of contacts: for $10 it's $0.01 per contact, for $50 it's $0.0005 per contact, at $150 it's $0.0006 per contact. For $50, they'd want the user to send/receive less than 5k messages to break-even on Twilio retail costs.

The main problem they will have if anyone tries to send to 100k contacts, is that Twilio limits the send rate to 1 sms per second. This batch will take 27.78 hours to send and 250k will take 69.45 hours to send. Not to mention that it will cost the company $1,000 and $2,500 respectively (although they will have a way better deal from Twilio than $0.01/sms at that point).

You're assuming they're only sending from one phone number.

Hrm... that's probably how it would work in most cases, as it would be confusing to end users to sign up from one number and get a text from one they don't know about (even if the footer text indicated who it was from).

This pricing issue is one of the reasons I could never justify pressing forward with my initial idea of getting in to this market. Someone will end up being the "constant contact of sms" - that seems a logical market to pursue, but I'm not sure how to get there with the current pricing models (I mean in general, not specifically sendhub).

This is the major disadvantage of using longcodes (regular 7 digit phone number) and is the reason that any company that is serious about sending out large quantity of messages, is using a shortcode (5-6 digit number) which can (with twilio) send up to 60 messages per second.