Midrash su Levitico 27:12

2) "unclean": to include (in redemption) a dead (literally unclean) beast which he consecrated (for its money value). I might think that (it is redeemed) even if he said "This beast is consecrated" and (then) it died; it is, therefore, written "then the beast shall be stood … (Vayikra 27:12) and the Cohein shall valuate it." Where there is "standing," there is valuation; where there is no standing, there is no valuation.

6) (Vayikra 27:12) ("And the Cohein shall valuate it, good or bad. As the Cohein valuates it for you, so shall it be.") "And the Cohein shall valuate it, good or bad.": Consecrated animals are not redeemed by approximation, (but there must be an exact estimate). "As the Cohein valuates it for you, so shall it be": If one said: I will take it for ten selaim; another: for twenty; another: for thirty; another: for forty; another: for fifty — If the "fifty" backed out, his property is attached for ten selaim; if the "forty," his property is attached for ten; if the "thirty," his property is attached for ten; if the "twenty," his property is attached for ten; if the "ten," the animal is sold for its (market) worth, and the balance is made up by the "ten."