Foreword: Sorry if too wordy, sorry if my estimates are floating (I include lots and set sales data), sorry I have used a sort of moving average estimate from other sites and ebay history which gets deleted.
I have found large differences in price between selling locally (often much smaller prices e.g. I got an alternate november for $50 USD, baby licorice for $90 USD in auctions) and selling internationally (much larger prices achievable) so there may be a big jump in Ebay prices or with other trading sites. So I try to use a price boundary and look to the average or gauge any marks blemishes rust etc. This is rough estimates based on sales I have seen and checked. If ebay and other trading sites ever unlocked more history records that could accurately be sorted into classification that would be awesome but the data centre costs required would be huge.
You have done really well noting marks, wear and tear etc and your prices look to be within my low high boundaries for quite a few. There are some things that can be harder to remove like identifying what kind of blemishes they may be. Pony cancer, rust & smooze tiny black spots, paint and light surface ink is much easier to remove then say deep set highlighter & marker ink, bleaching, sun burning, regrind or the dreaded benzoyl peroxide staining, (which seems to defy even paint fixes and I have not found a local supplier for the chemicals to counteract it; sadly brought one pony which had liberal use on non photographed areas, it is Quarantined).
Heart Throb: Ouch she can be a tricky as locally and internationally her price can be rather low e.g. 1-5 to high for her e.g. average high 15 depending on condition. Hair and symbols play a big part for her but when she appears in a lot I often don't count her or put a fixed 5 est (harsh but her glory is in my heart & memories but not as much in others). You mention she has her original curl which would make her on a much higher side and if her skin condition & symbols are good then even going for a 20-25 as more likely. Some local sales have been on the even higher side though due to lack of access to a nice version with factory curl so in this case a local trade with limited access or online site with less notoriety may be better to sell higher (if ok to wait, otherwise Ebay for faster time to sell but it does usually mean lower price for heart throb... unlike most other ponies the early ponies can be exceptions as they were widely sold).
Sand Castle, Shovels: If you sell the ponies as a pair or with accessories they can be worth more for each than trying to sell them separately but it is harder to find a buyer looking for both in an incomplete set (trade offs on the ease of finding a buyer versus the price you can set). So sand castle and shovels can sometimes go quite cheaply alone e.g. 15 locally, 25 low end to versus a pair at 75-90. setting a price for them would be best to start higher internationally so if you do sell them one at a time you have a bigger market. It might even be good to keep an eye to shifting their prices so they are around the current listed international ones so if there are only ones at 65+ listed in Europe like now then going for similar or a bit lower would give you an advantage in sales (especially for shipping) and then when other local sellers offer more you can consider adjusting the price alongside others.
Gardenglow/ garden glow: seen her sold super cheap in a lot with few bidders where other ponies carried the price more, and cheap locally 10 - 15. It can be that tricky lavender light purple and long hair tangles that can cause variation. I would set a higher price for her, wait for a bit, then bring it down for sales or offers. But even then perhaps having her in a lot e.g. sister ponies lot, would be worthwhile where her addition would increase the value of the other ponies around her more; their price would increase to larger and hers would be much the same as a solo sale. Hmm I think I just described a JRPG super skill attack/ally boost.
Jem Rama Llama: hmm watch this space of recent auction, this would be a good guide to find out what this one sells for to get a recent price
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Satin 'n Lace: I have seen a lot of flocking damage to hooves and ears ignored by international buyers when it comes to pricing so softs as this is common in small amounts on so softs and can be easier to repair. Unless chunks/larger patches of head or foot are missing don't worry too much. But oh drat marker on a so soft, well at least it is only on feet (assuming on underside) and she is a rare sosoft. I would price on the higher side of sosoft crumpets internationally in an auction (as in really on the high side, above 200 at minimum and even then higher). She would be a good one to experiment with a high auction price and then bring down in later tries.
It can be a real mix up as I remember one sosoft satin lace sold in a lot for lower (she was not mentioned in listing name but was there via symbol check) and one selling by itself but ebay scrubs the records way too soon. Sorry my current bug bear is to document and log the photo history (so I can compare and read back cards, boxes, accessory sets or pony color/discolor variations) instead of sorting the prices with a listing name/image check/lot division estimates & through a hand rolled query service that does daily polling of pony sales automatically (hmm this sounds easier than the photo sorting though... drat now I want to do that but but my picture checking and pony restoration jobs cry out).
I think Blue Rose estimates are good. They may not have lot sales included but that would take more time to split lot costs and would ruin the accuracy of the data (being mixed with other ponies or items) hence the individual pricing they have would be more accurate on solo sales. Perhaps on the high side (say an international sale solo compared to some lot sales) and for the low data point in the average perhaps too low (perhaps a local only sale with less bidders) but trying to find that metadata around sales or split lots would be impossible to log for now. Blue Rose efforts are pretty incredible amazing given the effort, the accuracy and what they have provided.
Edits: spelling and grammar
). With the sosoft having a lighter hair color and difficult to rehair when it may eventually go white perhaps a mid ground between non sosoft and magenta..