For raw compute, Fargate is ~1/2 the cost of Lambda. But you'd have to orchestrate the launch yourself. It could be worth it though depending on your workload
Shameless plug: I wrote AWSets[1], which can be used to do some of this (although the graphs aren't as pretty). It was written because at work we regularly interact with hundreds of AWS accounts and wanted something to quickly scan/catalog all of the resources (launch blog post explains more [2]).
It's free to run locally (doesn't use or require Config), the data is normalized & output as JSON for you to do whatever you want with it. It has better coverage than similar tools (>250 resources & growing), and provides relationship mapping between them as well. It's still a work in progress and might have rough edges, so feel free to file issues to help make it better.
Author here - This is a project I've been working on for the last several months that has proven to be quite useful. I finally got around to getting it open sourced.
AWSets is (yet another) tool for listing AWS resources across all regions in an account. The differentiator here is that it also builds relationships between resources. It still has some rough edges and will continue to receive steady updates, but I'm excited to get some feedback on it and see what the community can do with such a project.