I have heard from people who paid for a Jepsen test that he is eye wateringly expensive (and absolutely, rightfully should be, there are very few people in the world that can conduct analyses on this level) but maybe achievable with a gofundme.
I am not sure, for the same reason, that designing a DIY Jepsen suite correctly is really achievable for the vast majority of people. Distributed systems are very hard to get right, which means that testing them is very hard to get right as well.
He provides a good and unique service. He's worth every penny. Note that for some companies, the real "expense" is dedicating engineering hours to fix the shit he lit on fire in your code.
I am not sure, for the same reason, that designing a DIY Jepsen suite correctly is really achievable for the vast majority of people. Distributed systems are very hard to get right, which means that testing them is very hard to get right as well.