The point was in the form of a question. But there is some funny data around regarding P-8A OEW. The unofficial world is unanimous on 138,300 lb which sounds way too high. There is no official number I can find.
The original plan was to use the 737-700, but that changed to the -800 - 20 feet longer - to accommodate the APS-154. The structure has been beefed up for low flying and to carry multiple 1500-lb weapons under the outer wings. All that costs weight.
Also, the MAD was thrown out at the same time MTOW was nudged up a bit.