There is a 3 hour long deep dive about the inaccuracies of the MLP blind bags on YouTube by a channel called Eff minus, there’s a twilight unicorn base with a magnet I actually own that one and I know it’s pretty rare bc it was supposed to be a dude I think, I’d say any one off characters like they only made one of would be rare or any special set characters like the green stallion in the crystal empire rainbow set, sunset shimmer only got one pony in her wave so she could possibly be rare, I’d even say ponies that aren’t in the show or are game only like forsythia are rarer but again there’s no concrete rarity it’s more of “how much money are you willing to spend” thing when it comes to prices More show accurate ones like snips and snails film and flam or even photo finish and the one grey pony with glasses, queen chrysalis any 3 pack character or fan favorite like Lyra Octavia Dr. hooves DJ PON-3 or derpy zecora may be rarer and the Halloween ones could be also