Is tar and grit expensive ?

bitumen or tar can be very expensive depending on which supplier it is purchased from for example jobling purser charge 1600 pounds a ton at trade price. As for the chippings or grit i would say 200 pounds a ton average unless it was a specialist stone. These prices are for a company to purchase so depending on your surface area it could be very expensive.

tar is cheaper.

tar & chip is only a surface dressing for existing asphalt and tarmacadam areas if you want to lay it on a hardcore mot type 1 sub-base forget it choose a gravel shingle stone