Adding that much friction is also going to loose you many genuine users. Might be worth it depending on the community but if it makes newcomers fewer than your usual churn rate its a death sentence.
I think a better approach would be to upload an image to the sign up form with explicit instructions that isn't in text on the page to be easily read by AI. Like "Answer 2 in the Math captcha" even though the correct answer is 5, the AI will always enter the wrong number.
Where I live a 2nd class stamp costs the equivalent of $1.24. That's $1240 for a thousand.
Not including the cost of the letter itself, or the envelope, or the cost to write it if it's being farmed out to overseas labour, who then has to send it by international postage. And then you have evidence of where the letter originated, and that can be compared with how the user presents themselves online.
Little bit more than 2 hours minimum wage I think.
This is fucked and I hate it. Internet is (was?) about convenience and direct access. I understand there are challenges that need solutions, but this ain’t it
Not that I don't take your point that such a service could exist, but the site you linked explicitly says they don't offer letter writing as a service.
Also, I imagine it's not impossible to reliably distinguish between an autopen and genuine handwriting. The company who's site you linked say their machine can't perform complex pen movements so calligraphy is impossible.
The real advantage of posting a letter is that you have to pay for postage, and the stamps on the envelope will indicate which country the letter is really coming from.
If someone buys or makes something like this just to send a letter, they a) put in more human effort than writing it themselves, and b) are probably interesting and would benefit your community.
I think what robostwantdata was suggesting was that people would supply a "Use my mechanical pen for a fee" type service, where customers send the text they want written and the address they want the letter sent to.
As I've already said in my direct reply, there's still the various costs involved in posting the letter, and if the community is based on a particular geographical area e.g. "Connacht Hill Farmer's Association", then it would raise eyebrows if the envelope had a Kazakhstani stamp on it.