Main Menu -> Settings & Tools -> Tools -> Offline Cache -> Update Prices.
Or wait for 5.6.16 which is with Apple for review and in the hands of beta testers too.
is there an expected date when this update will be done? The trick you suggested to see offline prices does not work and/or is not always accurate.
It works but you have to pay money for it. I cannot answer for Apple but normally around a week.