I also seen this yesterday, although I don't think the $1500 limit included the cost of packages that Princess includes in their "Best Fare Package" . I was trying to add $500 worth of Casino credits, those for some reason weren't available so I just added $500 to my shipboard account, which put me over $2000 if the Best Value package was included. I'm still wondering what happened to the availability to purchase casino credits.
Maybe to close to sailing date, possibly? We depart 4/30, on the Ruby Princess.