I doubt that you will get 200fps increase with an AI barrel. And don't forget the hassle of fire-forming cases, much more expensive dies and such. That said, why do you want to rebarrel?? Poor accuracy?? Wrong contour?
The correct answer on the rebarrel job is: Do you plan on keeping the rifle? As you stated, the rebarrel will cost you close or more than a new rifle. Money which you will never get back if you sell the rifle. Most folks that are interested in a used rifle could care less that it has a premium xxx barrel. They want to know if it goes bang when you pull the little, hangy-down thingy underneath. And if you start explaining to them that the rifle has an AI chamber, their eyes sorta glaze over.
And you have no guarentee that you will like the new rifle any better.
On a rebarrel, even with a mid-range cost barrel, if you have a good smith do the work, you often gain considerabley in the accuracy department. However, as a rule, the .223 is so accurate "out of the box" that if you are a shooting crows and such and informal paper punching, the gains would be rather nebulous for your purposes.