Well look right at the top of the page you linked. $400 for a 2.9L double roller timing chain, chain only no tensioners. Double Roller is completely unnecessary for a 2.9L and a GOOD single roller with tensioners (Cloyes) can be had at RockAuto for ~$60.
Valve cover rails are unneceaaary if you take the time to straighten them (you'll have to do that either way if bent) and properly torque them in sequence. They get bent from being overtightened, either when installing new gaskets or tightening stock gaskets trying to stop a leak. Once bent they will keep leaking until you take the time to fix it or replace it.
Their "superior" valve cover seals for $95 are actually Fel-pro permadry seals available at RockAuto for around $40.
I could go through nearly every page on the site and pick a part a lot of the items.