True Cost

True Cost will help you to evaluate your spendings not in abstract dollars, euros or other currencies, but in units, understandable to everyone. You will be able to evaluate them in time units, which you need to earn this money.
Money made a huge contribution in humanity development – without it, trading and labor specialisation we could not reach the current level of well-being. But with advantages there are also some negative factors – we lost a direct link between time spent to earn money and products and spendings, for which we pay with the money. Non-cash money and credit only exacerbated this problem. It is hard for us to adequately perceive virtual cash amounts and convert them in working hours or days, which were required to get this money.
Thus it is better to spend several seconds and calculate the True Cost of planned purchases or spending
For more accurate calculations it is better to subtract your obligatory monthly spendings (housing, food, transportation, etc.) from your salary. You could do it in Settings. 
Expenses view allows you to value monthly expenses and shows how much "free" time you have.
Cheat Sheet will help you to remember real value of your times, so you will be able to make simple and approximate calculations in your head.
Also since we usually increase our spending with increases in salary, it could be a good idea to make these calculations not with the current salary, but with the previous one, or even the first one. 
Those, who are fortunate and successful enough and want to spend more consciously, could set as a Salary some lower amount, for example, average for the city or country, or maybe salary of your parents. This way previously minor purchases will be more significant. 
Since information about Salary and Spending amounts is very sensitive, you could protect it with a password (or with TouchID or FaceID).
All data is stored only on your device.