if the official Turkish rule is £6 per kilo
As I said before, this has nothing to do with the airport, it's staff or Turkey. That is the work instruction given to them by the airline they are the handling agents for. Excess baggage charges have been in the schedule airline side of the industry since aircraft went in to commercial service. It's nothing new but is now becoming more prevalent in the charter sector because of the economic climate. The charging is often negotiable and they will waiver some baggage, but that's at their discretion.
Just to give you an idea of the reason for excess luggage charging (sorry, going a little off topic here), I'll use a Rolls-Royce powered Boeing 757-200 as the example which is what Thomas cook often use to Turkey. The figures quoted are not absolute, but near enough for this purpose. They have a fuel capacity of 34,000kg giving a range of 2,600 miles (with fuel reserve). MAN-DLM is roughly 2,000 miles. The aircraft would therefore use around 27,000kg of fuel each way (ie, a lot!). The maximum take off weight (MTOW) are approx. 108,860kg. Therefore, fuel is approx. 25% of the weight of the aircraft depending on the passenger and luggage load. For every 4 kg of weight on the aircraft, 1 kg of this is fuel. Therefore to carry your 10kg of excess baggage, the airline needs to add 2.5kg of fuel. Imagine if every passenger or couple did this. With up to 235 passengers onboard the aircraft, if half of them had 5kg of extra luggage that would equate to 590 kg of excess luggage. I'll not bore with with the physics of flight, but the more weight on the aircraft, the more lift is required generated by a greater the angle of attack (wings) and therefore drag. This increased drag means more power and therefore fuel. This would require an extra 148 kg of fuel. At $130 a barrel, fuel costs are considerably more than they used to be. That is why airlines are clamping down on excess luggage and are being more strict. They can't absorb the cost anymore. There is a high markup on the charges, but as stated above, it's about discouraging people bringing too much luggage.
Darren