I do not believe one can say that there's no such thing as too high a price when that same person complains other people are wanting to pay too low a price. The market is subjective. Value is determined by an agreement between buyer and seller. Beastkeeper's community is so small, we could hardly even be said to have an average market value to gauge the worth of items. And besides, when some people are giving items away for free, it can make those who sell the same items at extravagant prices appear very greedy indeed. But that is all a matter of perspective.
I think many event items were overpriced, but that is only because I have my own idea of how much I would pay. Personal supply vs demand, if you will. For instance, as a newbie I was hesitant to pay more than 1,000 silver for a pet. Just a couple days ago, though, I bought a unicorn for 55,000 silver and still think I got a bargain.
If you don't like the price someone's offering, don't sell to them. If you don't like the price someone demands, don't buy from them. The RNG of Explore is another matter, though, and I do feel sorry for those who had terrible luck.