"I don't follow you, what's the difference between their product and the generic ESP8266 modules?"

I've tried to find out about the difference but wasn't succesful. Company "antratek" sells wifi3 too

Their offering is combination of the ESP8266 and a break out board for GPIO. Both cost less than 2 euro on ebay.

I also wanted to know why it is such big difference in the price and asked producer a question. Here is what they explained:

The board with Wifi 3 clik has mikroBus standard and written examples for their compilers, which makes it easier to use on all developing boards that support mikroBus standard. Also, they say, they give lifelong technical support for all their products. They have a growing community where their developers and users publish examples on all their products.

So, advanced users probably don't need any of that, but for less advanced maybe it could be useful.

At a quick glance it looks like their own clone of the reference design. I see nothing significantly different from a 2 euro model.