If Quark pushed Odo too hard, though, he'd lose the sale completely. Odo wasn't going to be stymied in his acquisition of the baby changeling by mere financial considerations. If the price was outrageous, Odo might have the Bajoran government or Starfleet intervene, and Quark would lose out on the transaction completely. Remember, the last time Quark reported a found baby, Sisko confiscated the entire
wreckage in which it was found! So maybe Quark took a "loss" on the baby Changeling in order to prevent the authorities from inspecting whatever else he acquired when he found the baby.