With some exceptions, and depending on how badly some one wants to buy/sell, vet rewards run somewhere around 500k per year last time I was in the market (tho it has been a while.) Koi Pond is 10th year, so I would expect to start haggling somewhere around 5m. Again, this is just my rough estimate based on what is probably out of date info. It is still fairly new, added only last year for 20th anni, and this is the slow time of year - both might effect value right now.