I do not have insight into all you are asking about, but I can try answer a few of your Qs. Others with experience may have a different take on it...
I think the waters get a little muddied on compensation. One can get paid through monetizing videos with ads, but I believe Bud also had sales agreements with every one of the vapes he reviewed. In that case, he was compensated for purchases that used the links at the bottom of his videos. In that latter scenario, I bet Ghost owed him a ton of money for sales that were generated and "clicked" through Bud's videos.
Outside of that, if one has "influencer" status on social media sites like instagram, there will be further agreements for compensation, just for posting about it. Some work off a handshake, but the most successful influencers use pretty tight contracts that cover compensation for pics versus videos, frequency of posts, events of default, etc.
I also agree that a "reviewer" should mention if they are getting compensated. I have not watched his videos in a LONG time, but I do believe Bud used to mention his compensation at the end of his segments.
I have done some product testing for this industry, but I have much more extensive testing experience with RC aircrafts. I share my thoughts on forums when I think there is something relevant to add, but I don't write traditional reviews for posting. Constructive comments go straight to the manufacturer before the public, then perhaps will repost some of those thoughts after a release.
That said, I can unashamedly tell you that all products I have worked with across both industries are given for testing at no cost. Understand that more often than not, products are delivered before pricing is even set. I know you think that may skew perspective and create bias, but it really does not for many honest reviewers [I know, not everyone is honest]. Many just can not flatter when it is unwarranted.
Product development and production is LONG. There has to be someone to put it through its paces, identify flaws and offer constructive criticism for improvements. Before you invest in large production runs, you want to make sure more people get products to test so that you can identify any quality control variances across X many units. One tries to address any and all issues before going into a larger scale production run. Obviously this example above is GROSSLY oversimplified, but you can see how during that period, there are usually quite a few test units that go out.
I do not recall ever requesting to test, I think more often reps just look for active posters who have a lot of experience. I've worked with devices from reps I knew, some that I became friendly with after years on FC, and other reps who were completely new to me.
I would add, that if this is a road you want to go down, have fun and keep it light. It can be a lot of work and turn into a job if you want it to. If you want a start, I have seen YoCan looking for new testers recently. Try posting them a note and see how it goes. Keep putting yourself out there and it will happen!
