Selling a Java desktop program?

Question

Java

There is a desktop program written in Java using JavaFX technology.
I want to sell it for Windows, Ubuntu, Mac OS X platforms.
The program is in the archive, without an installer.
So far, I see the purchase process as follows:
1. The user selects the program on the site
2. Pays
3. He receives a key by email
4. He enters it in the program
5. The program contacts the server and if the key is correct, it starts
I don’t want to fight hacking bother because the price is small $5.
Also, I don’t want to spend a lot of effort on the infrastructure for generating / issuing keys, accepting / confirming payments.
What sites/platforms are there to sell the program?
So far found:
https://weebly.com
There is a website builder + a store where you can sell programs. The situation with key generation is not clear yet.
https://invisionpower.com/
Forum + store. As I understand it, there is a key generator and the ability to verify them on the server.
Both options want $30-35 per month, I want something more budgetary...
Please share your experience in implementing programs.

Answer 1

If 40 ye is too much for you, then you should create a promo page and sell through it
Manually send keys