Richard.
https://epartsconnect.com
Live realtime stock market prediction website. https://www.stocksignalslive.com my latest creation. Uses AI and machine learning.
New site featuring ESP8266 and ESP32 projects. tutorials, and news.
http://EverythingESP.com
ESP8266.com Founder and Administrator
The Mind Factory (get more from your 3D printer)
Home of the ESP8266, ESP8285, and ESP32 microcontrollers....
But... if you are going to build 4,000 of something that is not a development board, it is better just to build it and not use a module.
Vocore made a decent profit on this (but he still hasn't shipped). Vocore is one man company.
https://www.indiegogo.com/projects/voco ... -with-wifi
I'm guessing he cleared an average of $10 an order times 2,951 orders = $30,000. Not a great profit for the amount of work involved. He still has to put 2,591 orders into boxes, address and mail them. Plus Indiegogo takes 9% (?) before he sees anything.
Bottom line - these RT5350/ MT7620/ AR9331 based systems are like 100x more powerful than a ESP8266. So if you are building something complex - use one of these chips, not a ESP8266. These chips all run Linux. So you can easily run a web server, python, SSH, UPNP media server, USB camera, USB Z-wave, USB BLE, etc, etc..... All straight out of the box using OpenWRT plus some other open source code. It is like comparing an Arduino to a Beaglebone.
I mean you can blink an led from a JVM if you want. I like the idea of maximizing the potential of the esp8266. I know you said complex, but most iot things aren't complex.