2,5$ - https://www.aliexpress.com/item/HLK-PM03-AC-DC-220V-to-3-3V-Step-Down-Buck-Power-Supply-Module-Intelligent-Household/32586663935.html
I don't use crap $2 esp8266 - https://www.aliexpress.com/item/D1-mini-V2-Mini-NodeMcu-4M-bytes-Lua-WIFI-Internet-of-Things-development-board-based-ESP8266/32529101036.htmlD1_mini best choice IMHO.
And don't think about money - I can eat in restaurant for 100$, but it give me less fun, than building my devices, it's a hobby.