Why buy something that isn’t built?
When buying from a developer you don’t pay transfer fees and the most important financial incentive for buying from developer is that bank will finance total cost of house, including VAT’s and all fees.
Buying from developer means you are protected by the Consumer Protection Act, which does not apply when buying from private seller. The act gives consumers more protection and imposes greater responsibility on developers to look after their interests, specifically because buyers cannot see the finished product before signing the contract
You can also influence the final product and variations in price to suit your needs, eg: Choosing the colour of the carpets, curtains, tiles etc.