Re: cost or costing? anyone
The "cost" of something is the price to be paid for it. "Costing" generally refers to the process by which one decides on what the cost is going to be [although in some contexts it can also mean the price paid, for example, "I bought two apples, each costing me 50 pence"].
Taking your two questions:
1. If the list includes details of how the price of each item has been calculated, it will be a "Costing List". If it is simply a list of prices, it will be a "Cost List".
2. Again, it depends on how much detail is included, but (assuming only one value is quoted) the correct usage is "estimated cost".
I'm not a teacher of English, but I have spoken it for (almost) all of my life....