You are mixing landowner profits and developer profits. Developers want low prices for new land in greenfield areas that will make the resulting houses appealing. Landowners want high prices but they also want to actually be able to sell - it doesn't matter how much your land is theoretically worth if nobody wants to buy it because they can't build on it.

1) House builders are big land owners;

2) The price of the land is passed on to property buyers in its entirety.