The "SHAPE@XY" token doesn't return an ArcPy Point object, it returns "a tuple of the feature's centroid x,y coordinates." Line 15 of your code replaces a Python tuple with an ArcPy Point object, which is what I am guessing is causing the error on Line 16. Does the code work if you update Line 15 to:
row[0] = (306400, 4098400)