Not sure how much a KA8 would be...
It's hard to quantify the usage, every house heating is different, house type size, windows, insulation, number of radiators, size of radiator, BTU requirements, location of the stove, boiler, etc...what kind of chimney or do you need to install one also, that is additional cost.
Do you have a place to store the coal, either in the basement, garage, etc...a easy way to load into a bin or room in the basement. Bagged is more expensive but can be stored just about anywhere. Check to make sure you can get coal locally, unless you plan to get it yourself from a supplier.
Some homes may only use 3 ton, others may use 6-10 tons. Even if you used 6 ton at around $200/ton on the average, that's only $1200. Still probably cheaper than Oil...the initial cost will be a bit high, but your payback will probably be 2-3 years.