The entry level option is the Raspberry Pi Zero 2 W, which is still $15

https://www.raspberrypi.com/products/raspberry-pi-zero-2-w/

It also has twice the RAM of the original Raspberry Pi (at launch), plus WiFi, plus a lot of CPU power, and a powerful GPU, and a lot more.

I have a 16GB model and I use that much RAM for some specific development work on the Raspberry Pi platform, but now I wish they had never announced the 16GB model. It has created so many complaints from people who shouldn't and won't be buying it.

>which is still $15

Let alone has it been hard to acquire for 6mo+ now, it's out of stock until mid-2027. Of course, can find sales for $115+ on ebay.