US-based vendors charge 4-5x more — are you paying for quality or convenience?

From the other side of the consultation, briefly. It helps to ask what evidence would change your mind before you look at any. If nothing would, the discussion is not about evidence, and it is better to say so early than to spend nine posts discovering it.

Ask again with the specifics and you will get a better answer than this one.

DataDave said:

One practical note: write down what you did and when, before you need it.

Coming at DataDave’s question from a different direction. It is worth asking what the claim would look like if it were false. If nothing would look different, it is not a claim about the world and no amount of discussion will settle it.

Adding the numbers, since they settle part of this. The boring version of this is the one that works, and the boring version is: measure a baseline, change one variable, wait, measure again under the same conditions. Nobody wants that answer and it is still the answer.

One thing that is still open after DataDave’s answer:

How long did you give it before you decided it was working?

Moderator note: a couple of off-topic posts removed.