"Hey guys, I'm looking to buy 10 BTC from a reputable seller. I'm willing to negotiate the price, but I'm thinking in the range of $45k - $50k for the entire amount. Has anyone got 10 BTC to spare or know someone who does?"
"Hey OP, saw your post and I got 10 BTC to sell, but my price is a bit higher than you're looking for. I'm thinking 50k for the full 10, but open to negotiations. Hit me with a lowball offer if you think you can do better."