Just by looking at a few WiFi service cost examples in the previous post, you might begin to see that there’s a lot of apples & oranges (and pineapples, and …) to compare. And a lot of circumstances (like sale promotions) that might lower your actual cost of WiFi service on a cruise ship.
On the various cruise lines, you might be charged: by the minute; by bandwidth, by paying for daily or voyage-long packages, or choose from tiered usage packages with various prices based on the types of sites & online service levels (sending emails… streaming shows…) that passengers use. Check carefully to ascertain what exactly you will get & for what price, & especially if WiFi service is really important for your travel plans.
Though I personally have not booked WiFi for a family all staying in one cruise ship (sleeping) cabin, in recent years I have noted WiFi starting prices that sometimes seem to add up to about $80 for each day, for a 4 person family.
By double checking current prices & doing a little starter math for your own specific cruise plans, you might see that adding the extra cost of WiFi service from the cruise line (to your basic cruise ticket price) might add up quite quickly.