bumper alone isn't very expensive to make and fab up, so you'd have to undercut a lot to get a prospective buyer to jump at it over just ordering the set new. It might not even be enough to cover the cost of an OEM bumper to replace it (assuming your OEM mounts aren't altered during fitment. On a 4Runner, my guess is they aren't, but you'd have to research).

Find out who makes the bumper. Then we can look at it's value and how it's mounted.

It looks like a quality piece. I'd keep it and if you don't like the exposed clasps for the beer cozys, then see if they have a cover piece to cover it.

It *is* superior to factory Toyota in every respect and if you decide you eventually want a swing out (you'd be surprised at how much better they are, functionally, for the vehicle), you are thousands of dollars ahead of the game.