Just make all the STEM programs FREE.
Making one program free while the rest remain expensive (all subjects should be free like they are in school) is not a good way to motivate students to take a STEM degree. You will end up with lots of poorly motivated students who cannot afford to take the subject they really want. The best way to ensure that students want to take STEM is to ensure that there are lots of well paid jobs waiting for them. This provides monetary incentive to people planning to make a career in STEM which is what you want.
The problem with society today is that STEM is viewed as hard by most students and leads to a job which is ok but requires real work. Compare that to the view of subjects like business studies or law where the view is that you can get a well paid job and have to do far less actual work to get the same (or even better) salary. That's not to say that there are a lot of really hard working lawyers and MBAs out there but the general perception is that you can get by doing far less work if you want to and still get a better salary than a STEM worker at least based on my interactions with prospective students.