What I would do is put that hobgoblin warlord's plate mail "front and center" in that encounter. The lore about hobgoblins say "Organized and disciplined, they take exceptional care of their weapons, armor, and personal possessions." The image of the warlord on page 187 shows the hobgoblin in some badass samurai-esque get-up.
When the fighter and paladin lay eyes upon this warrior, I'd describe the armor in a tantalizing fashion - its superior craftsmanship, its fearsome look, a work of art as much as protection for one's body. Once they're salivating over it and fighting over who gets to claim it when the battle is over, I lay the challenge down:
Because of the way this hobgoblin relies upon his armor to keep himself alive while he fights fearlessly (even recklessly at times), each time he takes 10 or more damage from an attack, the armor requires 150 gp of repair to be able to fit either of the characters.
Then kick off the fight and see what the players do to win the day while minimizing damage to the armor. This will probably lead to some clever actions on the part of the players to balance out victory and cost and those are the sorts of meaningful decisions I like to have in my games.