Have you put them on yet?
If you were just putting on the exhaust you would not have to change the jets, it would be slightly lean but it would be ok. But if you also add higher flow intake then your fuel mixture will be too lean, and the pistons and heads will overhead - you will need to have the jets changed if you do both.
You wont really get much of a HP boost with just the exhaust, but it will sound uhm.... lets call it different.
If you change both and have the jets changed you will increase the HP of the bike, and reduce your mpg fuel efficiency.
I cant help you with a cost estimate for doing the jets. If you are going to change the intake and exhaust yourself you can do the jets yourself too. Its just nuts and bolts and screws.