header question

[white eagle]

I see the other post on installing long tube headers and that brought to mind a few q's.
I was also looking at l/t headers for my 04,5.7 f150
the only l/t headers I could find were 1500.00 for the set.
I see the link of parts list these at a fraction of that price other than price is there that big a diff in headers to warrant that much cost difference ?
(I would rather not list the name of the other set)
What kinda gain do I actually get from this type of install?(other than the pleasing rumble)
I tailor wood (16'tandem)and a boat(17' fish and ski) and need all the power I can muster