For business/simulation games (take Lemonade Tycoon as a recent example most people have probably seen)... Is there a standardised/preferred method for modeling the math interactions?

Activity A brings in X*(Skill C) amount of money.
Item B costs Y amount of money and raises skill C by Z.

How does one work out the optimum values for numbers X, Y, and Z, other than throwing a lot of numbers in and playing the game until it all seems to work? :)

papillon:that's pretty much how it works from what i heard :)
One thing to note is that when you change a value, it's often fine to change it by 100% and test again how the changes work... that's what I heard Sid uses :)

This might help. I remember reading in the post mortem for Age of Empires that they used an Excel spread sheet with all the values of items, damage, points, etc, in the game. During play, a user could pull up this file, make a change, and submit the change while the game was running. This way the developers/testers/etc. could tweek the game. This also helps you to keep everything organized into one large table. Later, you put it into whatevery file format you want.

Good tools are key when developing this type of game. It must be possible to very easily modify values while the game is running, and also, it must be equally easy to directly see the effect each change have. Spending some time designing and implementing good tools and good feedback mechanisms, is usually time well spent.