Critical thinking includes not suggesting that someone should prove a negative. Those are independent benchmarks with the sole 'violation' of being re-posted on the vendor's site. Unless you can provide metrics that disprove them, they stand.
You could just pay for a license if you're that paranoid. It's remarkable to what extent people will complain about free not being "free enough". I assume you haven't contributed a line of code to the project, so it's a bit presumptuous to knock it.
How many companies can possibly afford the cost and management pain of running a 285 node database? Few would have 285 servers of any type? So if this is what it takes to get 1M writes on Cassandra that is some poor ROI. 10K writes/sec is not impressive.