I found your conclusion a bit misleading and unfortunately a lot of people often comes to the same conclusion.
Indeed the CPU is limiting factor in your bench, and while you say you're comparing apples to apples, it's not true in my opinion.
Maybe I'm wrong but I never see these actors as really competing in the same market : of course if you're looking for the best CPU perfomance/price ratio AWS is one the worst choice. But that's not what you're paying for imo, as someone already mention you're paying for the programmatic access, the ecosystem, the auto-scaling ability, monitoring, etc.
Move to AWS if you need the "Elastic" part in EC2 (Elastic Cloud Compute) or if you know what you're doing and what you're paying for.
Same for DO, what you're paying for is the SSD, they're advertising about it everywhere, so it's kind of obvious that a big part of what you'll pay for is the SSD.