Forum Discussion
Please see https://forums.swtor.com/topic/938907-maintenance-update-coming-january-30th/#comment-9842316.
Basically, on January 30 EA updated pricing for cartel coins and non-recurring subscriptions based on current exchange rates. They have not yet updated recurring subscription pricing based on current exchange rates and apparently will not until they provide 30 days notice to players who have an active recurring subscription.
In short, what you're seeing in terms of the pricing discrepancy between 60-days non-recurring and the recurring subscription rates is intentional, not a mistake. If you want to keep subscription to SWTOR then best advice is to use recurring subscription option for better pricing, at least until the recurring subscription rates are updated which in your case of the Polish Zloty would be a substantial (>2x) price increase.