Bangalore property: Real negotiation limits and hidden costs

Soppahalli keeps coming up every time I shortlist something. Currently in a 2BHK, looking to upgrade to a 3BHK or villa for investment. Kya lagta hai, builders like 42 Estates se kitna negotiate kar sakte hain? Pre-launch deals, are they actually better ya bas hype hai? Hidden costs ka bhi darr hai.