You can post as many numbrs as you like - but they all have to be considered in direct relationship to the installation or potential installation that is being considered.
For new installations all of the potential operastional costs - including decommissioning are rolled up. Given that most of the 'easy' fields have been exploited that means that the more difficult ones have significantly higher costs - some of which will be potential or 'risked' costs. Hence the care for new fields. With so many of them being HP/HT the risked costs can be very large. HP/HT wells are quite liukely to require expensive workovers before the installation design life is reached and that can be massively expensive.
On the other hand, old installations so long as they continue to turn out a reasonable level of production (circe 4000 barrels plus per day) make sense to continue running - if only becuause it means you do not have to reach very deep into your pockets and pay for them to be decommissioned! In these cases the cost of transport of all kinds starts to be pretty critical. So when the economics are run that 'modest' increase in costs is the straw that breaks the camel's back.
Costs are increasing in the N.Sea and that increase really does threaten a lot of the older installations. The overall inflation of costs for labour, support of all kinds and transport will make some of the older installations uneconomic and there will be a general reduction in logistic services. It is simply a question of inflation versus time.