The costs matter, but also permission. I'm essentially running small DDoS attacks and measuring performance under potentially heavy load. If I just signup and do it without permission, I could negatively impact other customers. That would be unacceptable ethically for me. There is also a lot of security measures in place to block these kinds of tests, that without permission, the tests would look like:
https://wphostingbenchmarks.com/company/aleforge/ their LoadStorm test. They weren't willing to turn off security measures and it blocked most of the requests. Impossible to tell what a non-attack looking load would experience, but because of testing tools sending large amounts of visitors from a very small pool of IPs, it appears like a DDoS attack and security measures block it.
Also thanks :) I am glad you find the work valuable!