Arduino just announced their latest product, the Nano ESP32.
There are 2 variants. The standard version for $20, and a variant with headers $21.Nano ESP32 packs Wi-Fi®/Bluetooth® connectivity, 8 MB of internal and 16 MB of external flash memory, 512 kB RAM, as well as a USB-C® programming port and RGB LED. It supports 5V USB, 3.3 V operating and 6-12 V range power supply. All in just 45x18 mm!