What nobody tells you about hidden property costs

Hidden costs in property buying are way more than anyone prepares you for. I'm looking at a 2BHK in Kogilu or Hosa Road, maybe a Prestige project, and my budget is around ₹78L for the flat itself. But ab samajh nahi aa raha ki upar se kitna aur kharcha hoga. My parents keep saying prepare for 20-25% extra, but that feels huge. Stamp duty, registration, interiors, GST on some things... is it really that much? And under-construction project lene mein bahut tension hai. Prestige ka track record toh sahi hai, but delivery delays ka darr toh rehta hi hai. How do you guys evaluate the actual delivery risk? Pehli baar khareed raha hoon, so thoda nervous hoon. Has anyone else faced this shock with the extra costs? Any advice on how to budget for these beyond the base price?