What they don't tell you about Chandigarh price negotiation

Budget finalised, loan pre-approved – now stuck on how much I can actually save. I'm looking at a 3BHK in Mohali Sector 70, around ₹1.5Cr. Builders like Omaxe often say prices are fixed. Honestly, can you really negotiate? What's a realistic percentage off, like 2-3% or more? Or is it just wishful thinking for a first-timer like me?