That seems like a pretty typical price variation to me. Pro tip, If you book the OV & make final payment, and then the price of the balcony drops after final (which is also very typical,) you can no longer CANCEL without penalty, but you can purchase an UPGRADE & pay only the difference between the two fares. You will be locked into whatever perks you had before & won't get any new ones they might be offering, but it's a good way to get into the balcony if you don't mind risking that the balconies could sell out or you might get a less-than-optimal location. This is different from the bidding upgrade process. Call your PCC or TA to request the upgrade. You also cannot get any cash refund, so if the balcony drops below the price you originally paid for the OV, you're out of luck.