I am doing a short / cheap cruise (3 nights) and there was not a huge difference. I am not sure if I am correct but I believe the total AI fare is non refundable (?) where you can cancel your drink and WiFi upgrade 2 days before the cruise.
My cruise fare was only $270 PP and it was about $210 to add the AI so would have been $480. Worse case and something comes up last minute I'd rather have the lower non refundable cost and pay a bit more for the upgrades.
I recently added the Premium Drinks on sale for $57/night PP and Wifi was $23 ish I think so $240 vs the orginal $210 and we got "Premium" beverages. Although I was also confussed on the taxes/fees/tips on the AI vs the upgrade.
