Thanks for the question Boris - apologies for the slow reply.
I think the simple answer is to create stuff that people want! Preferably NEW stuff, that pushes the boundaries and gets players excited about the extended possibilities of what they could achieve if they own it.
If they feel that urge, they will find the money somehow -
but prices need to be reasonable.
The 'new thing' has to be practical to use and with clearly provable advantages, so good videos showing how it works and what it can do are essential.
And finally you need to be able to supply the demand when the orders come in, post quickly, and deal with any customer service issues that arise in a fair and prompt manner.
I think that's about it! Pretty obvious really. Even new ideas are not hard to come by - I have several every day, and many others do as well.
The difficult part (but also the part I find most interesting) is testing them to destruction! Very often an idea is abandoned after the first prototype - you find your Great Concept was a load of wishful thinking, not practical at all for some reason or another.
Even the ideas that get further down the road often hit a seemingly insurmountable barrier, in many cases after months of work. That's a big disappointment and tough to accept! They get put in a box, likely never to see the light of day again.
But I find even the failures (and most of my ideas are in that sad category!) have a special feature that can come back and be adapted or used in a practical model that DOES succeed. Or my design/making skills advance to a point where a previously insurmountable barrier can be overcome. Or I have a 'eureka moment' and take a new, previously unthought-of direction to bypass a problem, perhaps enabled by a new material or process I discover.
Rn'D: it's an endlessly fascinating process that I find really absorbing and satisfying, because the little triumphs along the way trump the inevitable disappointments. But it does take a huge amount of time, trying this, trying that, starting from scratch. And to have the time to explore new things, you need to be financially supported in some way.
I'm lucky that enough of my design ideas eventually turn into products which capture people's imaginations sufficiently to turn a profit. Their sales enable me to have the time to keep pushing into new territory in the workshop, and play/record the music I want when I get that urge too.
If I just had to rely on music it would be tough, maybe impossible! Especially in this digital age when musicians can't get paid properly even for successful original material via royalties, as in the past.
But the flip side of that coin is that digitization has democratised so many previously out-of-reach areas for most people - such as making complex industrial parts. We can now create them in our homes, with small affordable machines and sell them to the world via the internet - wow!
That's a wonderful thing in all areas of life, including harmonicas

It enables creative people everywhere to get their stuff to a global market. If it's really good and priced right, it will sell.