How much is excess baggage per kg?

Is there a restriction on luggage on seaplane from Colombo to Koggala?

According to the current situation SriLankan Airlines "Air Taxi" is the only service which providing a Seaplane service in Sri Lanka ;ACCORDING_TO_SRILANKAN_AIR_TAXI_SERVICE'S_BAGGAGE_REGULATIONSYou are entitled for a free baggage allowance of 10 Kg. For passengers connecting through Sri Lankan Airlines' international flights, the same baggage allowance on the flight ticket will be permitted (Maximum 40 kg. Payload applies for carriage on-board.Sporting equipment such as surf boards (max 6ft), golf equipment are accepted (subject to payload restrictions) Excess baggage -- You will be entitled for 40kg of excess baggage upon purchasing of an additional seat.Excess baggage -- You will be entitled for 40kg of excess baggage upon purchasing of an additional seat.(Information Source : SriLankan Air Taxi Service)