Finally in my new Gurugram home, but surprised by costs.

Just moved into my new 3BHK in DLF City Phase II last month, and honestly, the possession process was a shocker. Builder ne initial quote kuch aur diya tha, but final bill mein bahut saare extra charges aa gaye. Maintenance advance, IFMS, society registration, OC charges... sab add ho gaya. Yeh sab total cost mein kitna difference daal dete hain, koi batata hi nahi hai pehle. My ₹2.5 Cr flat ended up way higher. Should I have pushed harder on negotiation for these 'hidden' costs or are they non-negotiable? What's the real ground reality for these charges in Gurugram, especially with builders like Suncity Projects? Hope this helps someone avoid my surprise.