Your current gold amount
It would be nice to have a "price source" that references your current gold amount. Obviously it wouldn't be useful in auction operations, but would be quite useful in things such as sniper operations. That way you could set the upper limit that you would pay to either your current gold on hand or a percentage of same.
My workaround until this is implemented is to implement a ceiling manually with a custom variable. Helpful in Classic especially where I'm struggling to get off the ground due to also buying things for my main.
1. Add custom variable, give it a name (ex. mygold)
2. Set a value (ex. 10g)
You can now use it, as long as you remember to update it as you grow. Such as my Sniper operation: