Hi Mate,
John is right with the coverage, by the book it's 10 sq m to a 25kg tub. If spray applied you can get more and some people by hand do get slightly more also.
Mapei do a 20kg Tub so the coverage is 8 sq m.
The prices from most manufacturers will vary if you are looking for the topcoat to be coloured. The darker the colour the more expensive it gets.
Will PM you some prices