I cheated copiously in my AP Chemistry class in high school. Man, I sucked at chemistry. I dunno why I took the class. I ended up getting a 2 on the AP test, so the joke's on me--a wasted year/class that I didn't have to take.
I think there are two counter arguments, though generally I agree with your position:
1. If you signed a non-cheating agreement, then you are effectively violating contract.
2. If you want to be accepted to another program and you think your grades might have an influence on the decision to accept you. Then, I think you are on shakey moral ground, because there is an implied contract (and often express, too, when you fill out the applications) that the information representing your experience and abilities is a true expression of your abilities. It makes sense that an applicant for to an intense chemistry program should be expected to have excelled in chemistry or somehow show some skill in that area.
"Why should witlesse man so much misweene that nothing is but that which he hath seen?"