Years and years back, I remember her selling for $40 something.
Value, I'd say it really depends on condition. If her eyes are free of chipping, parrots are nice and bright, hair is soft, and body is a nice green, you're looking at $90 and up. Go even higher for things like nice unfading pink in hair, no paint or blush rubs, iridescent sheen present on eyes. She's a really cool pony. I'm sure you'll love her once you finally have yours paid up and in your hands.
Ebay has been interesting over the past couple months. I way overpaid on a complete twins set a while back, thought I'd win for half the high bid I'd entered. Then, on the other hand I've gotten a number of sought after ponies for a steal with all their little accessories. Sometimes you're just pleasantly surprised when an auction ends. I wouldn't let that mimic auction bother you at all. Some ponies you pay that premium for, and then watch end lower somewhere else, others you get lucky and snag a deal on. It all evens out in the end. 8)
*edit to add*
I saw the auction. That one had some flaws, the seller didn't have much feedback and the pictures were very fuzzy. That definitely contributes to much lower ending prices. (I get some of my BEST deals from brand new sellers who take bad photo's - but it'***** and miss). Two others sold at $128, and $91. Thanks for this post. When I visit my family I think I'll be digging out my extra mimic and selling her off.