I bought an esp8266 board off ebay thinking it was the absolute cheapest rock bottom price product for a microcontroller capable of wifi.
But now today I see a ESP32-WROOM-32E board on eBay, and it's half the price. It seems to be much more powerful.
So is there any point in developing with the esp8266 if there's a cheaper more powerful alternative?
It's up to your liking, id you're halfway done and it's a couple of devices I would say not worth the effort but if you are starting new and don't have any experience with esp8266 I would say take the time and spend it on esp32 because it's a newer and more enhanced chip, also cheaper, and will see support in forums for a longer time.
Please suggest a good dev board to buy off eBay/Amazon/whatever for the ESP32.
By the way I've never used a dual-core microcontroller before so I'm very interested to see how data synchronisation works . . . I mean do you just mark a variable as 'volatile' or do you need to lock a mutex? Or is there atomics?
Although I see a Raspberry Pi Pico Wifi here for less than 10 pounds too. Don't know what to pick.
If your only criteria is that it has wifi then obviously any of them will work.
Unless one of them has another feature you need then they are all just as good as the others. There is no such thing as a best microcontroller.
Well, you already have it so why does the fact that there's a lower priced choice matter unless you need more. If you need more, how many more? Quantity affects price.
you have it alredy, don't you?
It's like this when I buy a new car. A year later they change the look, pump up the motor and. . . oh, man!
I'm buying a few trinkets and putting together a circuit . . . not even sure yet what I'll make . . . I mostly write desktop PC apps and also program microscopes in my day job . . . but I want to put together a very cheap circuit with wifi and SIM so then I can start brainstorming about how to make millions off my cheap circuit.
A friend of mine is big into making his own ammunition and has an RS232 weighing scales, so we might hook that up and play around with it.
I've ordered a NodeMCU with the esp32 with two cores . . . I've written plenty of multi-threaded desktop PC apps before but never programmed a microcontroller with two cores . . . I mean is there two entry points? Something like
int main1(void) {}
int main2(void) {}
I'll be interested to learn if marking a variable 'volatile' is enough to ensure that both cores are synchronised.
So you have no idea what you're going to build but your primary focus is on how much the parts cost? That seems a bit backwards to me, but you do you.
I've written multi-threaded programs for desktop PC's with 40 cores, and yeah it's interesting and all, but it's way more fun trying to get the most out of minimal hardware, and even more fun trying to make it as cheap as possible.
Just because a product cost less doesn't mean they will sell the most. Normal people just don't act like that. There are other things like availability, quality and sustainability.
The reputation of some products found on eBay is poor. This is because products that fail finial test in the factory and should be thrown out end up being sold on such sites.
A lot of people trust the Raspberry Pi brand, and it is quite popular.
I made a wifi repeater with a esp32 but could not get any of my own code to work on one and the arduino software was impossible to stay setup for it i had a bad experience with the esp32 aned i purchased a lot of them they might not be all that great of a product has anyone had good luck with them?
Yes, ESP32 is a great cheap mcu, arduino core works great, it`s constantly updated and there is lot of support, libraries etc.
This is the first hint I have seen that implies than non-Espressif ESP32 chips are in circulation. It is not absolutely clear, however. It maybe just that the basic modules are not Espressif
NOTE:
The purple version uses the original Espressif ESP32-S3 chip
The black version uses the Clone ESP32-S3 chip
Eventually everything popular (and it seems even if not popular) gets cloned.
I once suggested to someone who wanted to go to production to just make a few boards, wait for them to be cloned, and then buy the clones cheaper than he could make them himself and resell 
Is the Raspberry Pi Pico W about twice the price of the ESP32? If so then it makes sense for me to use the ESP32 if my main concern is to keep costs down.
Also . . . I will have a passive buzzer on my board which I will need to alternate with a clock signal of about 2 - 5 kHz . . . it would be cumbersome to get this timed correctly while also doing other things in the superloop -- but since the ESP32 has two cores, one of the cores can be simply doing:
for ( long unsigned i = 0u; i < 8000000u; ++i )
{
digitalWrite(pin, i & 1u);
delayMicroseconds(200);
}
Another thing I will try to do is to try interleave the accessing of the SDcard, so that when I download a large file from the web server, one core is reading from the SDcard while the other is sending a packet out on the wifi.
I'm going to have fun messing around with a multicore microcontroller.
None of those things are difficult to accomplish on a single core either. TBH, the greatest benefit to multiple cores that I've seen is for safety-critical applications and separation of concerns.
Generating a clock signal with a period less than a millisecond can be dodgy if your superloop occasionally takes more than a millisecond to iterate.