You guys are going a little steep.
I bought one of these loadcells for a test: https://www.amazon.c...1_O0gozb0RDP7V8
My weigh plates are prototyped in ply wood for now. Basically I'm imagining 1/4 steel plate approximately 12"x12" or similar. 1/4 carbon steel plate is about $10 a square foot.
So I get this so far...
4x 1k loadcells = $200 - https://www.amazon.c...1_O0gozb0RDP7V8
1x RPi3 = $36 - https://www.amazon.c...1_L9gozbNQBY5F4 (could be swapped for RPi Zero W for 10 dollars less)
4x Loadcell ADCs = $8 - https://www.amazon.c...1_z.gozbGZ390B2
1x PCB = ~$12 - Prototype boards in low quantity can be ordered in minimum of 3 units @ approximately $37 dollars (Optional cost, you could wire the electronics with no board)
8x steel plates = $85 - any local fab shop should have something like this; no leveling mechanism
Misc hardware = $20 - bolts, etc
Each set of plates requires 3 holes to be drilled for mounting load cells that can be done yourself.
Total cost is $361.
That is bare minimum, but we could actually work on this platform and extend functionality etc. I don't know if the other scale companies even have a phone app wireless interface or ability to store measurements etc, but they definitely are not on their entry level products. Honestly with a little more work and another $100 in electronics we could even have wireless battery powered pads.
If anyone has an idea of how to get the cost of the plates lower that would be huge since electronics are already dirt cheap and load cells probably won't be easy to get cheaper.
In the end this is just an experiment for me. It's entirely possible that we can't beat the manufacturers that can keep costs low with mass production.