I think those prices look good
I would pop black tie Pinkie up a bit - she was pricey to buy due to coming in sets. Perhaps more like $6 for her.
For Star Swirl - $50 is perfectly possible but I think she is more likely to be $35-40.
Daisy Dream with the forelock again $8
The upper end of the estimate for Diamond Rose
Lower for Lyra, Sunny and Cherry - they were relatively easy to find and therefore are not far exceeding retail to be honest.
I would put Sunset Shimmer up higher - more like $6-8 - although common she is really popular.
Ploomette sits about $20.
Mrs Cake is a little lower and probably going to drop again due to yet another release; but the fact its always in expensive sets normally keeps her about the $6-8.
I would say lower for all of Lemony, Trixie and Flower Wishes - more $5-7
Star Dreams has now had 3 releases, she is not up at that value any more. However I would add a little extra to Twirly Treats - she is a popular little pony.