Disclaimer: this is according to my memory when I first became a crazy MAC addict!
I know you'd asked for ones that are highly sought after now but I thought I'd post previous ones so you can scratch them off your list, since you'd mentioned it's been tough keeping track of re-releases.
So Ceylon was until it was re-released (so thankful for that!). I'd seen it go BNIB for min $60, max $100. Used I'd seen with a $40 asking price. Perhaps it'd go $40 BNIB now? Maybe a bit higher b/c of the price increases.
Stereo Rose was another but it will be re-released soon with In The Groove.
Sometimes it was as popular as So Ceylon but I think there were more of this to go around so ppl went crazy after it but it wasn't as rare, lowering the market price a bit.
Porcelain Pink was a biggie but not as much as the other two. Let's say I would expect to pay $25 for used (got a great deal for $20 shipped tho!!).
Those were the ones I sought after most when I came into MAC around 2005. After that was Lightscapade and Petticoat but jets cooled on Lightscapade (I think b/c it's not as colourful) and Petticoat was re-released (to be re-released again).
Oh, and there was Gold Deposit as well but it came back as a mineralize rotation product. Prior to that I think it had similar status to PP?
HTH!