Salarpuria Sattva: Real negotiation possible?

Hi everyone, we're totally new to this home-buying journey and it's been stressful! We've been hunting for a 3BHK in Gachibowli for months, specifically looking at Salarpuria Sattva projects. The prices, especially around ₹1.5 Cr, seem so firm, almost like they're non-negotiable. Is real negotiation even possible with a big builder like Salarpuria Sattva, or are they just showing us a fixed rate? Also, beyond stamp duty and registration, what hidden charges should we really watch out for? We're on a tight budget, so every rupee counts.