I once spent some time building a SAAS app that would send text messages on a regular basis, up to 6 per day.
It was a consumer app, so I'd costed it at $10 a month.
Not great in terms of income, but it was in the weight-loss market, so the total revenue could have been interesting enough to work with.
So I spent a few weeks getting it built, then I realised something. I'd costed out using US customers (even though I'm in the UK).
US customers would run at 1.40 USD per subscriber per month. Not a bad mark-up.
But SMS messages in Belgium via Twilio are 0.10 USD per message.
0.1*6*30 = 18.00 USD.
Oops.
What about here in the UK? I'd be running at just over 7 USD.
So I canned that idea for now.