I just took up baking bread. I started with sourdough. If you keep the starter fed, you don’t need yeast. I’d say the cost for 2 loaves is about 80 cents plus elecricity for the oven.
Also, I’m a beer brewer. That means I’m up to my eyeballs with yeast.
I never tried to make sourdough bread. It does sound like it would be cheaper to make.