Items sold by the unit, What's the standard? Options

[Zolhex]

This is mainly for magical supplies that are sold by the unit so what is a unit?

Oricalcum 50,000 a unit?
Flowers (depending on grade) 50 / 100 / 200 a unit?

So on and so fourth so what is a unit 1 gram? 1 ounce? 1 pound? 1 kilo?

What should I as a GM say the amount of a unit is?

I get that it can be different for each item I get that it's a GM's call as to the quantity.

I guess what I am asking is if there is no set standard what do other GM's use as a mesure of a unit per each item sold by the unit?

Please post your thoughts and ideas maybe we can all come to an agreement that can become the standard then if a GM wants s/he can increase/decrease as fits their game and style.

Like for instance 1 unit of oricalcum is 2 ounces as a standard but in GM freds game oricalcum is a bit rarer so he modifies it to be 1 ounce. While GM shelly says oricalcum is readily available so it is 3 ounces. Mean while the main mass of GM's leaves it at 2 ounces because we as a community have by majoirty said this amount seemed reasonablely accurate to the way the story and/or rules are playing out.