It's bizarre to me that this is moving SO slowly. I expected media properties that are entrenched in nearly everybody's childhood from the last nearly 50 years would have more hard core fans a la Disney collectors.
There's a difference between being "entrenched" in one's childhood and being worth 300 bucks. Star Wars and Transformers are entrenched in many people's childhoods as well, but there are plenty of people who haven't touched a toy since whatever birthday or Christmas they were last given one however many years ago.
Collectors are always a small subset of a given genre, and I'd imagine multiple-hundred-dollar Sesame Street collectors are one off the smallest subsets there are. Like, I imagine there are high-end Muppet collectors, but Cookie Monster isn't technically even a member of the Muppet team.