I just saw an Ice Crystal that was complete go for ~ $450 USD on ebay in August.
The bulk of that cost is in the sticker and ribbon, the sticker alone can sell for well over $100
I would say around $150 for ice crystal at a push maybe $200
That is interesting about thundercloud, I would ask around. If the lighting is missing as a factory flaw it would increase his value. A nice thundercloud with no head body mismatch or cancer can fetch around $180, the prices come down accordlying to flaws, even a very flawed guy still sells for around $80 us these days
The princess and tall tails I am not sure about, I would ask in the nirvana section. I might be interested in primrose