In general, local currency prices aren't recalculated again unless you (the publisher) update the USD base price or update the market-specific prices. The customer sees one price throughout the lifetime of that plan or private offer.
Example: In a three-year deal priced at $1000/year, publisher has a USD payout currency and customer has a SEK billing account currency. We’ll assume the FX rate at point of price save was 1 USD = 10 SEK.
Applicable FX at the point where the price was saved in the plan/private offer results in this being converted to 10,000 SEK/year
Customer(s) will pay 10,000 SEK every year for the deal.
As a publisher with a USD payout currency, you'll be paid the USD equivalent of 10,000 SEK using the monthly WMR FX rate for SEK>USD that applies in the month of the billing cycle.
Note
All FX calculations in the examples are for illustrative purposes only