I see, the current price has deviated from the website's rates. $118.80 USD * 1.35 market rate = about $160 CAD, about $3 CAD of difference from my number.
So for your upgrade price, 79 EUR * 1.47 = comparable to $116 CAD. For me, my app says C109.22, which is about 6% less.
It looks like my prices should be in Canadian dollars, and the "all prices are in USD" is a misleading note or a bug (the sample menus seem to be in USD).
I was only thinking of getting SDP for the third guest to be able to dine together at Teppanyaki, but it doesn't look like a good value proposition for that since a la carte is $59 USD, and my SDP per meal is about $58 USD but I have to buy two meals.