Pre-launch deals: Are they ever really worth it?

Okay I'll be honest — I almost fell for a pre-launch scheme at Spacebook Estates in Chi V. I'm currently in a 2BHK, looking to upgrade to a 3BHK, maybe ₹1.5 Cr budget. They push these construction-linked payment plans hard, saying it's best for investors. But does early-bird pricing actually save you money? Or are there better deals closer to possession? I'm wondering if a down payment plan is smarter for total acquisition cost. Already have a home loan, so trying to leverage that.