Yes, it will raise the value.
You have to compare players with same quality, look at the price of scouts.
Depending of the quality the diference between levels can be 50, 100, 150K, and a bit more whend reching the next star.
I can say that at level 3 a 18 years old 5* costs around 5M, on level 4 8M, on level 2 i think is around 2,5 or 3M.