Lambda is a value-added service on top of EC2. It only makes financial sense to use it when you don't want something running constantly, or otherwise have a way to take advantage of the extremely fine granularity in billing. (Or if you're willing to pay a premium to have Amazon manage your process lifecycles for you.)
But, most of the post was meant as joke to see what I could push lambda to do.
To answer your final question: I wrote a spot instance automation tool, you can check it out at autospotting.org, so I would give spot instances a try. The latest developments from AWS on the spot market are real game changers, I think most of the workloads can now safely run on spot, my AutoSpotting tool makes it a breeze to migrate from on-demand AutoScaling groups while keeping them a bit more reliable than the native AutoScaling integration for spot.
As of a few months ago the pricing is much more stable than before, I've rarely seen terminations even over the maximum three months of history for instances that used to go bust multiple times a day. You also now pay them on a per-second basis, and you can hibernate the last one to keep the state of the group while everything is down.
So my approach for this would be to have an AutoScaling group of the smallest spot instances that can run your app, scale them to N nodes right before your experiment, then when you're done scale down to a single one, which you use as data seed next time, which you detach and hibernate with API calls.
Next time you re-attach the seed to the empty group, and scale out to N once again and run your test. So you only pay for the length of your test on a per-second basis.
You can also keep the seed as an on demand node outside of the spot group and have it run from the free tier if you still have some time left, or just hibernate it as well.
For folks long despairing that our programming environments have been stuck in a rut for decades, we're about to be hit by both the opportunity to reimagine our compilation tooling, and the need to rewrite the world again (as for phones) for VR/AR. If only programming language and type systems research hadn't been underfunded for decades, we'd be golden.
 https://github.com/StanfordSNR/gg ; video of talk demo: https://www.youtube.com/watch?v=O9qqSZAny3I&t=55m15s ; some slides (page 24): http://www.serverlesscomputing.org/wosc2/presentations/s2-wo...
It was built exactly to deal with a high level of churn, specifically for edge computing with spotty network. So yes it does.