These are all very interesting questions, thanks. We have actually given this a lot of thought, so let me answer one-by-one.
For sales and fulfillment, we have tried many different models. To have a fulfillment service provide basic fulfillment we would need to provide a lot of training, and then the cost to you, the end-user, would need to increase by about 20%. Also you would be looking at much longer fulfillment times, and much less intelligent and helpful people answering the phone. This just didn’t work for us (we tried).
We could try a distributor with specialized knowledge, which we also tried many years ago with Dr. Pawluk, but they too added a huge margin to the cost, and at that time the A9, and earlier models, sold for more than $1000(!). That was not working for my objective of providing affordable, reliable, personal PEMF, so we changed that relationship, have more recently tried to re-structure it, but it is rocky, and they sell the A9 at or near our current price, but they have no incentive to market it because the margin for them is just too small. You will be happy to know this has been the problem with all potential distributors: not enough margin built into the price.
We eventually decided to do all of the fulfillment, taking orders, shipping, returns, and customer service ourselves. This results in much better customer service, as reflected in much better rate of sales for each time a person calls. We can do the work much more efficiently than an hourly employee or a service, so you end up getting better, faster, more personalized and knowledgeable service for much less than a 20% bump in price.
Amazon is something we are still considering, but it may be accessories only, since periodically there is a sweep of not-quite-FDA-approved products from Amazon if they feel any heat from regulators or competitors. Also, they add a fair amount to the price, which is why so many supplement sales dropped off Amazon during the pandemic.
For customer reviews, you have to also consider that the PEMF market is essentially a pit of snakes, and if you put yourself on Amazon, then some sock-puppet reviewers will just crucify you to boost the sales of their junky pirated pseudo-PEMF product (which was probably just directly copied from us anyway).
Finally, for Amazon, many customers really need a bit of coaching at the outset to get started, but Amazon tends to attract people who formulate an opinion about a product based on its packaging and appearance, before they even use it. Just check any Amazon reviews, soon you will find one like this “Looked crappy when it arrived a day late and was not obvious how to use it, and was not what I expected, but may change my mind in a later review when I get around to trying it… one star”
So, for a lot of reasons, Amazon is a “probably not” option.
eBay however works extremely well for us and it integrates well with our refurbished and slightly nicked product line, and we sell those on eBay almost the minute we post them.
As you know, people can still contact us at our original site (micro-pulse.com) and recently we do our fulfillment through fluxhealth.co, but that is still in the family, just my wife, me, and now Chris, who is Mark Tommerdahl’s daughter that we have known for years (decades).
Scalability? This has several different aspects to consider:
Manufacturing (DFM): My first degree and job was as a manufacturing/mechanical engineer. The M1 and A9 are definitely designed for large volume production if necessary. The B5 and C5 would need a minor PCB re-design and a new case design, not too much work actually.
I would tweak the designs a bit if it got really big, but basically the A9 and M1 are designed to be able to be manufactured with high quality in batches as small as individual units by hand, or in quantities of 10,000 or more. Pricing of course gets significantly better with higher volume. Let me know if you need a million A9’s. I could start delivery in just a few weeks and fulfill in a few months. I would even give you the friends-and-family volume discount for quantities over 10,000 
Scalability: Fulfillment - Just packaging and mailing is not a problem at high volumes. Customer service would be the real challenge at high volumes, as it typically is for any tech product (did any of you get to talk to Steve Jobs about your new iPhone, before he passed away?)
Growth: I just keep telling the truth about what I know (and don’t know), and that seems to be such an exotic unicorn approach to marketing on the Internet that we get pretty solid growth, year-on-year. It is a huge challenge to think about and plan for how I can manage it in the future.
