AA is unlikely to budge for liability reasons.
It has acknowledged responsibility for the shirt and will presumably live up to its commitment to pay for cleaning (or perhaps replacement if need be). As to you, the $25 gesture is clearly not compensation of any kind and is not intended to be, lest you change your mind, sue and then suggest that AA has somehow admitted fault for damage (beyond the shirt).
I am afraid that you are fairly well stuck here as AA is not likely to do more.