Developers can launch at whatever price they want. Once buyers come in, it will make the price "true". So far, these projects are selling, which makes it the new market price in a way, meaning the market is not likely to come down. For sure you won't see a new launch around RCR area near mrt going below 1.5k psf anytime soon that's for sure.
IMO, these are driven by strong marketing, with exceptionally high commission going to the agents, to raise sentiment and to drive up the market artificially. I do not think it represents the true value, but you can't fight the market. You have to accept it, or stay out of the game. It's your call.
On a side note, whether those developments you mentioned are all "near mrt" i don't know. WLR definitely is, JS and Stirling still ok, but P Clementis is definitely not near imo. Don't be fooled by marketing tactics.