Not sure where you’re from. But here is a random one from ebay . You will find many like it. I got this model with 4gb ram, 256 ssd and power supply for ~80€ on europe, much less then I could pay for any PI4 at the time that came with no case, no psu, no ssd. It idles around 3-4w headless with no peripherals running home assistant. There are other models too ofc. Just have a look around used hardware stores if you have them around your area.