I thought about doing a price comparison, but that gets really tricky. At some point, you're testing the skills of the tester more than the services themselves.
Agree with your expectations though. I think Fargate is naturally faster and can be moreso given the number of knobs you can tune. This will likely cost you more, both in direct resource costs and in engineering time trying to fine-tune the knobs. Whether that's worth it depends on your business needs.