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

The competent authority shall consider costs unreasonable where the cost estimate exceeds the benefit. To that end, the benefit shall be calculated by multiplying an improvement factor by a reference price of EUR 80 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 operator's 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 that would be achieved by the improvement multiplied by the average annual emissions caused by that source stream over the three most recent years.