Twilio is interesting because they're offering this as a business-specific offering i.e., integrate with Twilio directly (SMS, voice), which on its face is actually more valuable than, say, a "generalized compute platform" (which we've referred to ourselves as, at times). I think it'll be really interesting to see how Twilio markets + plays with this model --- theoretically if it sells their other services they could get away with this being a loss-leader, which is an intriguing concept.
I'm thinking you mean the COST of compute here. If that's the case, I actually disagree on cost trend direction. I think the raw cost of compute will slowly increase. Long story but most of it borders on the economics of cloud computing.
So you can figure out their loss/margin based off the public Lambda pricing model.
Lambda costs 0.00001667 per GB-s... so if each Twilio function used 1GB of memory and ran for 1 second, it would cost them $0.17 per month to serve you.
Since the max memory in Lambda is 1.5GB and the max runtime is 5 minutes... the worst case is that twilio is spending $75 for those 10k requests. I assume they were smart enough to use lower amounts of memory and set the maximum runtime of the Lambda function pretty low, like a few seconds.