Is it possible to buy a property in a place like J.J. Colony for less than the government-set price? For instance, if the official rate is around 4.5 lakhs, could someone buy it for just 15 lakhs? Would the registration process allow for such a low price?

No, under Indian law, property transactions must be registered at the actual market value, not a significantly lower price. The registration process requires proof of consideration, and a discrepancy between the sale price and market value could raise suspicion of fraud or tax evasion.