The weight capacity has NOTHING to do with this technology. You stick a copper wire through a steel block, you can read the current ~ and depending how many times (1 million, 100,000 or 10) you will get different qualities of signal out of that load cell.
You use a couple of pieces of polymer with a brass foil in the center, your quality will still depend more on your chip than on the load cell/strain gauge.
If I were putting together a bathroom scale I'd buy them by the hundreds of thousands and probably pay about 25% of what you'd pay for just one. The rest of the outfit can be put together in a toy manufacturing shop in Hong Kong or Guandung. They do all that sort of thing these days.
Assuming you don't set fire to the equipment the sensitivity of this form of weighing is dependent on deformation of an electric current. Good current ~ > Good signal.
The Postal sampling scales we were buying initially cost over $1000 a pop, but as that technology became more common that price dropped into the hundreds ~ but with a Postal Scale you need multiple read-outs and a set of precision leveling screws PLUS a set of standard weights ~ and they cost some money too.
Your typical bathroom scale can be calibrated at the factory and has a need for only one read out. It's also not varying the number of measurements taken so it can give you a weight with confidence to 6 digits to the right of the decimal point. But it could if you put in the read-outs and the balance screws.
I am still waiting for you to post the specs of a strain gauge that will output to one part in a billion ...
Please show me a link to your bathroom scale that goes to over 13,000 kg. Thanks.
Balance screws?