My post-possession hidden cost shock

Budget finalised, loan pre-approved – now stuck on hidden costs. Just took possession of my 3BHK from Green Pike Builders in Punjabi Bagh and man, the final bill had surprises. Things nobody tells you about until the last minute. Did anyone manage to negotiate past these 'mandatory' charges? Like the extra club membership fee or the sudden power backup installation cost that wasn't in the initial agreement. I mean, it added nearly 5L to my total. Wondering if others faced this, and if negotiation tactics actually helped. Should've asked for an all-in cost breakdown earlier, tbh.