You're right, the above posters generalize way too much. They are either CS or Maths students and as such are already well-prepared for self-study! If you study Maths you already know what all the symbols like epsilon, e etc. mean, you can just gloss over a mathematical text and get the gist of it. Same goes for many (but not all!!!) CS-students, some unis lean a lot on algebra, some don't do much maths after the first two courses.

As such, I think it's ridiculous to go up to anyone and tell him/her to just "study by yourself", I could give a maths book to a biologist and that person would understand absolutely nothing without guidance.

Well, you could certainly do it when you start with "Maths 101" or something like that.

I was addressing the money issue and tacitly assuming that they could do the work. For just a Bachelor's and then just a Master's in engineering, they have a good chance of being able to judge correctly if they can do the work.