Is pre-launch pricing worth the hidden costs in Gurugram?

Since last Diwali, I'm seriously fed up with renting in Gurugram. My landlord just hiked the rent again for my Golf Course Ext. Road 3BHK, and I'm finally taking the plunge to buy. I'm looking at places on Dwarka Expressway and SPR, targeting a 3BHK around ₹1.8-2.5 Cr. Matlab, I'm trying to calculate the *total* cost beyond just the flat price. Builders like M3M and Godrej quote one price, but then there's stamp duty, registration, PLC, parking, and all those hidden charges. Someone told me about OC charges too, which I never considered. Is it better to jump on pre-launch offers, ya phir wait for RTM? Pre-launch mein discount dikhta hai, but is that real after all the extras? What's the realistic all-in-cost for a 3BHK in these areas? Any experience with hidden costs popping up right before possession? Don't want any surprises.