To be a little bit of a contrarian,I'll toss in another viewpoint.
The fine ,experienced cooks above have multiple and varied uses for their scales.
Smokin' often asks "what is your specific use" as this may establish your need.
As mentioned,there is large variation in wood.Age,type,cooker.
My co-cook is a baker and a mathematician and has a need for exact replication.
I am more of a gumbo type cook.
Each takes a different approach ,but turns out a fine product.
If your cooker is a small,conventional Cookshack that is often used to cook a couple 8 lb pork butts,or a larger Cookshack 260,you might be well served with an under $5 approximate scale.
If you do wet chemical compositions,or exact dry weight combinations,you might be better served with a multiple hundred dollar weight/volume piece of equipment.
Just a couple of thoughts.