People who sell items for the fair going price aren't emotionally attached - they are just doing business.
If you have something that's worth about $200 on the market and you're asking for $2000 then you probably don't actually want to sell it. But if something is worth $200-250 on the market and you're selling it for $200 that's just... normal.
It's not arbitrary - most collectors I know keep track of the going rates of items they want so they can spot a good deal if it comes along. If one is going to spend hundreds of dollars on collectibles one better do their homework.
A lot of people list things with inflated prices on eBay to try to catch that buyer who either does not know better or really just wants whatever it is so much that they will pay some crazy price.
If you tell me which items you are talking about I'd be happy to tell you the current 'going rate' for them
Many non-collectors are surprised about the rate their old toys can sell for these days.
The SuperS henshin wand in that auction has sold for an average of $190 in the last 12 months on eBay with the highest being $255. Because of eBay and PP fees, items are often listed 15-20% higher than average on BIN prices on eBay. So that auction, while a bit high, probably isn't completely outrageous, especially if it were a very high wish list item for a collector. You're right, it will probably be there for a while. They either don't really want to sell it or they are seeing if anyone will go for it before lowering it to a more marketable price. That being said, if you REALLY wanted to sell one of those right away, listing it for something like $150 would make it go fast.
It's not really about being "sensible," it's just supply and demand. These things are long out of production and some of them are very desirable for collectors and fans. The more people want and item the more money they are willing to spend to get it because it becomes competitive. When more people want something the price goes up. If no one wants it or there are more items than buyers then the price goes down.
Such is the world of collectibles!