A few theories come to mind.
1. Developer's mistake: put simply, they forgot to account for an integer (5,000 -> 5,000 -> 500).
2. Game balance: maybe five K a pop of that filthy Amnian lucre is too advantageous for low level parties?
3. In-setting economics: with the Iron Crisis affecting the region, luxury goods become less desirable. Is that right? I would think the value would increase, if anything.
4. Underhanded commerce: the proprietor in Naskhel is pocketing a MASSIVE profit while fleecing the party from their rightly-deserved fair market value.
5. Hidden genius: as noted, the pelt must be in good condition. Riddling a Winter Wolf with arrows or roasting one with a Fireball (which are tactics utilized by quite a few players, I'd imagine) ought to mar their hide. Furthermore, unless one is a Ranger, Druid/woodland priest or anyone with substantial hunting experience, skinning a beast may result in a serviceable but not striking specimen.