The $99 offer happened because tourism was slow for two reasons :
The economy was very slow so people were not booking cruises
The events of Sept 11 caused many people to cancel existing cruises and others not to book cruises
DCL made an extraordinary effort to get people back to cruising again and it looks like it will be very successful.
The $99 offer was distributed to people that cruised on a 4 or a 7 day cruise that started during the month of January. Basically, it said that for every person that sailed on an eligible cruise, they were entitled to sail again on a 3 day cruise during specified dates in the Fall. You could not have more than the number that sailed in January and at least one person from the January cruise had to sail on the Fall cruise. The $99 offer specified that if you had a veranda cabin in January, you would have one in the fall, if you had an outside cabin, you would have one in the fall, and the same for an inside cabin. If you were in a category 1 to 3 cabin, you would be in a category 4 to 7 in the fall.
The cost of $99 covered the port charges and the guest would also have to pay the government fees and taxes, which amount to just under $29 for an adult, less for a child. You could add transfers and insurance, and I believe also the air.
In my opinion, it was a heroic effort by DCL to get people booking cruises again. The money they collect just covers the port charges, taxes, and govt fees. It was offered on a total of 8 cruises in January and it can be used on 12 different cruises in the Fall, so as much as 75% of the cabins could be filled with the $99 cruisers. I would imagine that I'll be so thrilled with my $99 cruise that I'll be a very easy sell for booking another 7 day cruise while on board, and others will be also.
hope that helps