Probably a 5-20% increase depending on fit and recommendations/essays.
I didn't see your economic situation so you should probably apply RD.
You may also want to ask the office because ED applicants usually get what they deserve in aid and in my experiences Carnegie Mellon will throw money at them or let them out of the binding ED. You should do a little searching and weigh your options before you commit.
I think your chances are good even if you do RD so perhaps you should just work on your essays/recommendations a bit more and get in that way.