You're forgetting quite a few variables. I would be willing to bet some of the resellers are holding onto the dolls, hoping they go up in value, rather than down. Some of them are holding onto the dolls until there's very few left on ebay, thinking that if there's fewer of them listed, there's less competition, and that may result in a higher price. Some of the resellers are holding onto the dolls, thinking a full set will sell for more than an individual set. And some of the resellers are holding onto them until Christmas time, thinking mommy & daddy or grandma and grandpa will spend more on them as a Christmas gift.
Also, there's more places to sell these dolls other than ebay. There's
amazon, Craigslist, etc. Even on the vinylmation trading boards and pin trading boards I frequent, there's people trying to sell them or trade them for high dollar pins & vinyls. So it's clear they only picked up the doll to off it for something more expensive, even if it's not money....