It is about people expectation.

When 95% of people expect A item price will be going up, you buy, I buy. You jack up price, I also jack up price, everyone do it, price keep on escalating.

Just like people said, price keep on escalating, not buy now, tomorrow higher.
Tomorrow not buy, after tomorrow higher
So die die also buy.

Mass people expectation is a powerful force.

Only until one day, people get burnt and lose in speculation on the expectation, only then this fever can be slow down.

Developers have nothing to lose, by keep on launching new project, as all risk are with properties buyers side. (when the project is sold out)
Housing or real estate is a strange product.
Whenever we bought a thing, we only paid money when the product is ready to use. Just like buying car, you only paid money when you bought the ready to use car aka completed car.
But house, you need to pay even though the house is 10% completed. Do we see car manufacturers demand 10% or progressive payment when car is 50% completed?

Also, nowadays, developers are more clever in launching project, by adopting 1st phase, 2nd phase, 3rd phase, at the same area, and one common thing I noticed, 1st is always the cheapest, and being sold out quickly, which give good reason to hike on price on 2nd phase.
When similar house on 2nd phase is launched at higher price, it pushed up the 1st phase house. And when 1st phase buyer make good money, it tends to people "greedy", and people will said/see, hey must buy, see how 1st phase buyers make decent profit, which prompt people to buy or rush to the 2nd phase, and so on on 3rd phase.