Most things cost exactly "1" unit to produce. 1 is always used with BOULDER or WOOD, TANNED_HIDE or regular objects. Some armour etc is supposed to cost more, but a bug means it costs 1.
Bars come in units of 150, as do some other types such as drinks, liquids, powders.
Cloth is 10000 and Thread is 15000. you might have notices there figures in-game if you try and make something from cloth, in the announcements.
For 10 stone reagents you want a line like this :-
[REAGENT:stone:10:BOULDER:NONE:NONE:NONE]
And a product like this
[PRODUCT:100:10:CHAIR:NONE:GET_MATERIAL_FROM_REAGENT:stone:NONE]
The only issue here is that the reagent might pick 10 different stones (haven't tested the theory) but the product will all be of a single stone type, probably of the first selected stone. If it does happen like that, it could be avoided by copy/pasting like this (for 5 items):-
[REAGENT:stone1:1:BOULDER:NONE:NONE:NONE]
[REAGENT:stone2:1:BOULDER:NONE:NONE:NONE]
[REAGENT:stone3:1:BOULDER:NONE:NONE:NONE]
[REAGENT:stone4:1:BOULDER:NONE:NONE:NONE]
[REAGENT:stone5:1:BOULDER:NONE:NONE:NONE]
[PRODUCT:100:1:CHAIR:NONE:GET_MATERIAL_FROM_REAGENT:stone1:NONE]
[PRODUCT:100:1:CHAIR:NONE:GET_MATERIAL_FROM_REAGENT:stone2:NONE]
[PRODUCT:100:1:CHAIR:NONE:GET_MATERIAL_FROM_REAGENT:stone3:NONE]
[PRODUCT:100:1:CHAIR:NONE:GET_MATERIAL_FROM_REAGENT:stone4:NONE]
[PRODUCT:100:1:CHAIR:NONE:GET_MATERIAL_FROM_REAGENT:stone5:NONE]
The above will produce 5 chairs while remembering which stone was used for each one.