The ESP32 (with Bluetooth and WiFi) is like $5 on AMZN. Which is probably sub-$2 in any meaningful quantity in Shenzhen. We've been living, at least until the tariffs, in a StarTrek like world where whatever we want is available from Shenzhen for a ridiculously low price (which in many respects is better than "free" because "free" brings with it its own humongous problems).