Another option that's used often in analytical laboratories for the same reason: stock solutions!
Since you want to use fairly cheap ingredients, you can create a "stock solution" (in water1) and measure that with much more accuracy.
In your case, you can measure 10g each of salt & yeast, mix them with 80g of water to make 100g of a stock solution2 containing 10% by weight salt and 10% b.w. yeast. You can then measure 10g of this with fair accuracy and add it to your dough, effectively adding 1g each of salt and yeast.
The main downside of this method is that you are wasting salt & yeast to make the stock, but seeing as they're both fairly cheap I don't see it as a dealbreaker. The other point of attention is that you're adding a bit of extra bulk ingredient (8g of water in the above example), which you might need to take into account at some other point.
1: You can substitute water for flour, or any other bulk ingredient, however solid ingredients require very careful & thorough mixing for the above method to work
2: More accurately it's a dispersion as yeast doesn't really dissolve