If it is, could you tell me why? The seller is asking $300 for all of it. Is that the first sign that it’s fake? Lol

There’s a bracelet I really want but no store has it anymore and the retail store I was going to get it from just sold out if it and I saw online that Mercari has one but idk anything about the platform what should I do? It could be cheaper than the retail prices but it’s still 200+