Facts:
 * I am a foreigner living for 2 years in Germany.
* I worked for a company for 1 year and changed to my recent company
* I really enjoy working here
* I have 10+ years in sw development
* I really thing (honestly) that I am an employee that anyone would like to have due to my enthusiasm and work quality
* I speak German fluently

Situation:
People brought to my attention that students job posting were offering a similar hour based salary than mine (from the same value up to 4 euro less). But I dismissed that for a while.
Now many people on my team decided to quit (for different reason) and on this context of leaving, farewell parties and so on I got the information that people with no prior experience were receiving just a little bit less than I do and some people with same age and a little bit more experience were getting twice my salary.
I got very frustrated because I have lots of responsibilities and I do my job well and I was repeatedly told by boss.
Now I scheduled a meeting to talk about it because it just extinguished my motivation and I have he feeling that they used my lack of knowledge of the job market to give me a low salary.

I will ask for a big raise, so I am nearer to the ones my work is similar to.

The thing is: many people of my team are leaving, in two months my team will be reduced to 2 people (me +1, and I am older in the company). I do not want to use this as a pressure tool. But I will look for alternatives if we do not get to some number that I am happy with.
How do I tell them that, without sounding as a threat and being known as someone who used their delicate situation for my benefit?

PS: my company is really well financially.