Upgrading with points

I should know the answer to this but the move to dynamic pricing has made me question everything!!!

If I book an EC seat at a (frankly ridiculous) high points level such as 30k one way becuase I need the flight that day and PE is stupidly high, then later they reduce points for both EC and PE and I want to upgrade, do I pay the points difference between what I paid and the new PE, or the new EC and the new PE?

I'm just trying to work out if I really need to hold my nerve a bit longer for the flight that I want! Thanks

You would pay the difference between the points you paid originally for Econ and the price of the Prem seat.

Cheers, so if PE has been reduced to lower than what was originally paid for EC presumably you are just charged the extra taxes?

You would be charged the extra taxes and fees and if PE is lower than the Econ you bought you would be refunded the points over i.e bought Econ for 50k points, PE is 40k, you would get 10k points back.