Based on all those economic courses I took years ago, who pays the costs really depends on pricing power.

For example, if there is a shortage of gas the producers will have pricing power and Coastal Gaslink will have to charge less in order to attract the pas and so it will absorb the costs at that time.

But if there is an excess of gas and all the producers want access to the pipeline, then Coastal Gaslink will have the pricing power and it will make the producers absorb the extra costs.

Then again, if there is a world wide supply shortage, both the producers and Coastal will have the pricing power and the Asian buyers will absorb the cost.

In practice, prices, supply and demand will fluctuate over time and a variety of the players will absorb the extra costs in different proportions over the long time period. Most of the time they are likely to be sharing the costs in varying proportions.

But that is just my take from some professors years ago.