Have you tried Step Functions? I've used them to orchestrate Lambdas with good success when I needed something that will run longer than Lambdas can individually.
Yeah, they’re good, but more expensive than you’d expect given the relative pricing compared to other AWS services. $0.025/1000 transitions seems and order of magnitude or two high given it’s just ultimately a central job store with some very, very simple logic for changing state.
Step Functions are convenient but for the reason you stated we stopped using them. Pricing seems off for what they do, especially when it's in volume.
I wrote a simple lambda function that takes in a payload and a step function arn. It then fires up a bunch of step function jobs and maps the execution identifier to the input and stores that in s3 for later access. This ends up being really nice for creating distributed cron like jobs by just connecting the lambda to cloudwatch events.