You've a good point about the EMR charge - that's easy to overlook.
I took a look at Whirr [1] but I don't see how having a cloud-agnostic platform helps - are there really alternatives to EMR out there? Can they give me 500+ cc2.8xlarge equivalent machines on-demand but at spot prices?
[1] Assuming this is the Whirr to which you refer: https://whirr.apache.org/