Noida pre-launch offers: What's the real catch?

Budget finalised, loan pre-approved — now stuck on which sector. I'm eyeing a 3BHK in Sector 150 ya 107, aiming for max ROI, not just end-use. Gaurik Green Homes ka ek project Omicron III mein dekh raha tha, they're pushing pre-launch offers. But I'm not sure if early bird pricing is actually a discount ya bas hype hai. From my experience, sometimes later stages mein builders better spot discounts de dete hain, especially if inventory clear karna ho. Kya kisi ko real numbers pata hain pre-launch vs open market price difference ke? Also, construction-linked payment plans are attractive for cash flow, but is it smarter than a down payment for long-term gains? Aur possession ke time hidden charges ka kya scene hai? Stamp duty, registration ke alawa kya expect karoon? Builders often spring up maintenance, club, power backup charges at the last minute. Koi experience share karega?