I don't think your proof works. If you spend $8000 and several weeks recruiting a marketing manager, you're paying for someone who knows what to do and how to do it, because you don't know how and/or don't have time.
If you go to a web site that does A/B testing, you're going to get a set of instructions about how to install it on your site, and then it's up to you to figure out what changes you should try. You now how more work to do, and no better idea about what you should be trying.
If you really do have a way to replace a full-time marketing person with an automated web site, build it. It will be a gold mine.
I'm not saying that there isn't a person out there who can revolutionize my marketing in 20 minutes. I'm saying that I have no way of evaluating someone's marketing skill in just 20 minutes. That's why it's expensive and time-consuming.
If a web site charged $500 and was very easy to implement, I could do it as an experiment and not lose much if it failed. If it succeeded, that web site could charge me again and again to keep doing it, and I would be happy to pay.
But if I have to spend $8000 and several weeks up front, I'm going to be very cautious. It doesn't matter if that money and time are spent hiring someone or purchasing and installing an automated tool.
Note that I defined/proved the non-existence of a market at $5000 (in exchange for 20 minutes of any operator's personal time) and you countered by claiming a (possible) willingness to pay at $500. Thus proving my point. It doesn't really matter what reason you gave, which in your case was trust. Ordinarily that could be countered with escrow or a lack of up-front payment, but this still does not happen, that market still doesn't exist. You can't pay someone whatever revolutionizing your marketing is worth, after you've given them a chance to do so in just 20 minutes and seen, "yep, that works". Doing so would feel wrong to you.
"I'm not saying that there isn't a person out there who can revolutionize my marketing in 20 minutes" - I'm saying you wouldn't pay them to do so in line with what doing so would/should be 'worth' to you. There is no market to pay to revolutionize your marketing in 20 minutes, at a pricing that is based on what it should be worth for you to do so. Doesn't exist. You wouldn't pay it. Imagine what "revolutionaizing your marketing" means, image what "revolutionizing your marketing" would be worth to you - do you have that figure in mind? Now imagine paying that to someone for 20 minutes of their time. You wouldn't. Neither would anyone else. That market doesn't exist.
If you go to a web site that does A/B testing, you're going to get a set of instructions about how to install it on your site, and then it's up to you to figure out what changes you should try. You now how more work to do, and no better idea about what you should be trying.
If you really do have a way to replace a full-time marketing person with an automated web site, build it. It will be a gold mine.