I guess you're paying a 5x premium for Lambda in the constant usage scenario, a similar premium as on-demand vs spot instances.
4GB m6g.medium $0.0385/hour
4GB Lambda works out at $0.1920/hour
It's been a while since I last used queue driven autoscaling groups, but https://aws.amazon.com/blogs/compute/scaling-your-applicatio... has startup time of about 4 minutes from scratch or 36s from a paused instance in a 'warm pool.' vs less than a second for Lambda in the original article. So the decision ends up coming down to responsiveness vs cost. Presumably Fargate comes somewhere in between.
Technically, yes, but it's kinda missing the point.