No. Read it again. The $300 is for machining and parts for the installation on dovetail not pinned, "and dovetail sights like on the PC 627 and PC 686+ can take a lot of machining that generally runs upwards of $300 for the whole job." The point being, some front sights by S&W don't have ready solutions, such as the dovetail, so knowing which ones come from S&W with Tritium can be helpful.
Part of an e-mail from Bo Wallace, XS Sights, "You are correct we don’t have anything for the 627, that front sight dovetail is an odd one specific to S&W." And therefore getting something to work for the DOVETAIL sight can be very labor intensive if you find someone to do it.
Installation of a pinned front sight is comparatively drastically simpler and cheaper with the only potentially tricky part being the extreme small size of the hole and the difficulties associated with a drill bit that thin (such as for the 586 L-Comp pictured above). That potential problem can be relieved by drilling from both sides and meeting in the middle, but it still remains a simple and cheap job.