1. Where an operator or aircraft operator claims that applying a specific monitoring methodology incurs unreasonable costs, the competent authority shall assess the unreasonable nature of the costs, taking into account the operator's justification.

The competent authority shall consider costs unreasonable where the cost estimation exceeds the benefit. To that end, the benefit shall be calculated by multiplying an improvement factor with a reference price of EUR 20 per allowance and costs shall include an appropriate depreciation period based on the economic lifetime of the equipment.

2. When assessing the unreasonable nature of the costs with regard to the choice of tier levels for activity data, the competent authority shall use as the improvement factor referred to in paragraph 1 the difference between the uncertainty currently achieved and the uncertainty threshold of the tier which would be achieved by the improvement multiplied by the average annual emissions caused by that source stream over the three most recent years.