I think you are going to pay the extra amount. The whole point of the package is to split the room among two passengers. Why would they give you a "discount" for having one less person when you consume the same number of rooms, one.
References :

I didn't know they did that, that's terrible. You probably won't want to do this, but since gas and hotels are so expensive now a days, I switched over to camping. I have saved a small fortune so far plus I love it! You just need a tent ,air mattress, air pump and a good sleeping bag. I bought all this for under $100 and have used it a lot this year.

A camp site is usually around $10-20 dollars a night depending on location.
References :

If you book a tour and it states double occupency charges apply, then there is nothing you can do. If you simply traveled and got a hotel room yourself without a travel agency or tour package you could get a single rate.
References :

Not sure about Cruises but you can find a good airfare then create your own tour. There are many guide books like The Lonely Planet, Rough Guides, Frommers, Lets Go, that you can do your homework. You can find them in bookstores or the Library speciallizing in the location you desire.Then deciding on how much you want to pay for accomodation. You can stay in a dormitory style hostel or find a cheap hotel to a 5 star hotel.
References :

I think you are pretty much out of luck unless you find some one who wants to share the trip with you… You can try the B&B's and such if that is practical… but as far as the trip fare goes you'll be out of luck and have to pay single rates…
References :

there are tours that will match you with a roomate, but there's no way out of going alsone, without the fee.
References :

I think Sharon can help you: http://www.travelaloneandloveit.com/index.htm
References :