Been saving for years, is the premium justified?

Currently in a 2BHK in Sector 75, thinking of upgrading to a 3BHK near the Expressway. Is the price jump worth it? Already have a home loan, so EMI is a big factor. Heard mixed things about the actual carpet area vs advertised super area with some builders. Like, Supertech allegedly shows big numbers but the usable space is way less. Anyone experienced this? Honestly not sure if it's just marketing. Also, what about maintenance after possession? Heard some builders like ATS charge crazy amounts. Is it true? Is it negotiable? Don't want to get stuck paying extortionate fees after sinking all my money into a new place. What are your thoughts? Any experiences to share?