wvmarle:
The NodeMCU is at the lower end of that price point and has WiFi built in. Set one to host, the rest as clients. I think they can even do mesh networking between them.
Will it give reliable 200 m range? I know I got a pair of ESP8266's working at about 120m using ESP-NOW and clear line of sight. ESP-NOW is not WiFi and I have not done any range checks with WiFi. The OP mentioned trees - they are not good for 2.4GHz wireless.
I would expect the high-power nRF24L01+ modules (with the external antenna) to work at 200m, but they are not WiFi. If the OP is interested in those modules this Simple nRF24L01+ Tutorial may be of interest.
I think for reliable long range communication a lower wireless frequency - such as the 433MHz HC12 modules or LoRa would be better. But they, also, are not WiFi and they may be a little more expensive.
The obvious financial advantage of the ESP8266 is that it an work on its own without an Arduino whereas the other modules need to be connected to an Arduino.
The ESP8266-07 has a connector for an external antenna but I have no idea whether or by how much that improves its range.
...R