One important thing missing is the ability to specify approximate numbers, just like we do in real life.
Let’s say this item is going to cost me $90-120. I’d like to write down just that. Also I’d like to say that there is a 80% probability that I will be able to purchase the item for $90, 10% probability of spending $100, etc.
Then you can calculate all those estimations and probabilities and deliver a figure that is much more useful than just a =SUM() from an Excel table.
(I have used this method of estimation in software dev project management)
In my experience, I've found that plans and estimates (whether in software or life stuff) are always more accurate if you just use the higher number in the range. If anything, it still won't be high enough, especially for software. And even if you overshoot a bit this way, it's a lot better to miss high than miss low.
Let’s say this item is going to cost me $90-120. I’d like to write down just that. Also I’d like to say that there is a 80% probability that I will be able to purchase the item for $90, 10% probability of spending $100, etc.
Then you can calculate all those estimations and probabilities and deliver a figure that is much more useful than just a =SUM() from an Excel table.
(I have used this method of estimation in software dev project management)