I'm not trying to offer it as a service. I'm trying to run my workload in a way that can scale from 0 -> 10,000 request/second in an instant and doesn't cost my company $5,000/month to do so.
It's pretty easy if you know what you're doing (or care to figure it out).
If you can do $250/month with all ops costs and features of lambda for 5,000 or 10,000 requests per second - you would be silly not to offer a service.
There are plenty of us who can run a system that scales to 10krps. That's relatively easy? I personally can't stand lambda and don't use it FWIW. I like EC2, I actually like fargate a lot of all sorts of things including lambda like services without a separate lambda for each request.
But for folks with a payload, that want the lambda like experience - if you have a solution, all ops cost included (ie, no well paid developer or ops person needed for customer) for $250/month for the scale we are talking here (2,500 x 250MB = 625GB etc) then you have an amazing solution going especially if you can do the networking, IAM controls etc that aws provides.
The problem I've seen, when folks say amazon is "insanely expensive" they are usually not actually comparing the AWS offering to a similar offering. If your cheap solution is not lambda like, you need to compare to EC2 or similar (with perhaps a good programmer doing something a bit more monolithic than aws).
It's pretty easy if you know what you're doing (or care to figure it out).