>>6606196Experienced eBay seller here...
Prices can fluctuate depending on several factors. For example, if a popular Youtube creator makes a review or it's shown on a popular TV show or movie, then the price will rise. If the company makes a reproduction or a superior version of the doll, the old doll's demand and value will go down. It's basic demand, scarcity, etc.
Just because someone is asking for an obscene amount of money on eBay doesn't mean that they're gonna get it. Lots of times, sellers jack the price WAAAY up to catch that certain whale of a buyer with more money than brains. ALWAYS check the "completed items" option when searching for something's value on eBay. You can get a much better grasp as to what sellers are pricing items and how much buyers are willing to pay.
That being said, a quick glance shows that only that one seller is selling a Glam Midge and completed listings shows no Glam Midge doll being listed or sold. However, the search also shows most MIB Glam barbies going for a decent amount, about $20~$50, depending on the doll.
If you wanted to sell your own Glam Midge, anon, I'd advise you to put it up on a 7-day auction. Put the starting price at $40 with a Buy-It-Now for $100. Midge is a fan favorite, so I'm sure she'll get hit.