Side note, if you purchase items in a foreign country with a credit card, you should always purchase them in the local (foreign) currency and not in US dollars, and then your credit card handles the conversion. This goes for any country.
I wouldn't pay that much extra to just go to a JS either. That being said, we are a family of 4 (kids are 16 and 20 now), and we booked a balcony cabin on Wonder OTS for ~$5000. We put in some bids to "Royal Up" and were just awarded a Grand Suite for our bid. $3k extra (total) was my bid. We are very happy considering I didn't expect anything was available. Would've cost us at least 12k if we booked it from the start.