When I look at the Titleist custom options brochure, I see that for the 718 T-MB, it describes the Project-X PXi shaft option under upcharge as "Yes (No-718 T-MB)". I read this as there is no upcharge on the PXi shaft for the 718 T-MB yet all the UK retailers seems to have a charge around £12-£15 per club for this shaft. Which is correct?