Experion project: Hidden costs ka darr, koi help karega?

Sector 35 Sohna — I'm seriously looking at Experion Developers here for a 3BHK. Currently in a 2BHK in Sector 57, thinking of upgrading, budget around ₹2.5-3 Cr. I'm worried about hidden charges jo possession ke time pe aate hain. Builders brochure mein sab clear nahi batate, right? Kya kisi ko Experion projects mein aise surprise costs aaye hain? Maintenance deposits, utility connections, OC charges... these can add up. Pre-launch pricing ka kya scene hai? Log bolte hain early bird advantage milta hai, but is it actually a discount or just marketing hype? Matlab, when you compare to open-market prices later, is the difference significant? Super area aur carpet area ka bhi confusion hai. Kaise pata chale ki builder numbers inflate toh nahi kar raha? Already home loan chal raha hai, so I need to be super clear on the true all-in cost. Any advice on what to look out for?