If my target audience are the millionaires, with fortune over $25M each, what should be the shortest way to reach them, if my product can track severe diseases and prolong their life (doesn't matter if they have their own doctors / labs what so ever)?
Step 1: Determine where your target audience hangout, where do they spend most of their time.
As per your target audience, it's Reading.
Step 2: Connect with those high-quality knowledge sharing blogs/writers/etc get them to genuinely endorse your products in-between their knowledge nuggets.
Note: You could do advertising at those places as well, but that's nothing compared to an endorsement from the authority figure (from where/whom your target audience is learning.).
According to Forbes, there are only 173 K families (pre-pandemic) with $25 mm + NW in the USA. Having spent a ton of time in the HNW/Institutional/VC wealth management and investment spaces, be very prepared that you will have a difficult time cracking this community - like all of us that were not part of it to begin with. They do not trust, they assume you want their money, they are highly skeptical and deeply cynical - they all know those in their community that have been scammed and that gets everywhere fast.
Your only way in is via direct, content-relevant introductions (i.e. medical intro for you, not from a lawyer or accountant). Health is a big deal but they have the highest quality health care that can be found, so you must find a provider in that space that can refer you to them - or them to you. It may not matter to you if they have their own doctors or labs, but it matters a ton to them. Do not look at this market as people who are dis-intermediating anyone or anything; they use accountants, lawyers, and doctors because they trust them, not because there are no alternatives.
High net worth people seek and trust other high net worth people for referrals and leads to solutions, services, etc. I would think more about your $25MM threshold as the total addressable market of these people is relatively small in numbers. If you are going to truly focus on high net worth people, expand your audience by starting with people that have a net worth of $1MM. I am happy to talk through this with you. Thanks.
what is your app name please
Off the top of my head I feel you'd be most likely to see success by getting your offering in front of professionals or companies that these high net worth individuals trust (doctors, family offices, lawyers, etc) as opposed to presenting directly to the individuals themselves. Speaking from my own experience I'd imagine it would be possible as long as what you're offering is truly of value. Feel free to message if you want to discuss.