I've seen perfect torches for other classes go for 1.5K~. I'd imagine a perfect warlock torch to go for double that (~3K) because warlock torches are still in demand. Since this is one off perfect, I'd estimate 1.5-2K, but it depends on the buyer.
Lowballers are annoying, but sellers can also counteroffer, so you can begin a negotiation with an earnest buyer. It seems like a lot of sellers here take offense to lowballs and just ignore people, but you need to be able to discern lowball trolls from actual bidders that want to negotiate. Use your best judgement.
Softcore