The price of soldering station is very low and you can say that making of solder station is it not preferred.
You have right, maybe...
But, if you want to design our solder station, design of regulator takes a lot of time.
This project can speed up your project.
It main component is ATMega8. PWM controls power to solder station. Data are shown in 16x2 display.

There are schematic, PCB and firmware of project.
http://eprojects.xyz/2015/06/22/diy-soldering-station-part-i/
http://eprojects.xyz/2015/06/30/diy-soldering-station-part-ii/