how much money does a game designer make?

Great question. Fortunately the information is available here:

http://www.gamasutra.com/view/news/221533/Game_Developer_Salary_Survey_2014_The_results_are_in.php

Salaried game developers

In 2013, salaried game developers in the U.S. made an average of $83,060 last year, down 2 percent from the year prior.

Business and management salaries topped all other disciplines once again this year, averaging $101,572, followed by audio professionals ($95,682) and programmers ($93,251). Quality assurance professionals earned the lowest average salary at $54,833.

Here are the rest of the disciplines we covered (U.S.):
Business and management: $101,572
Audio professionals: $95,682
Programmers: $93,251
Artists and animators: $74,349
Producers: $82,286
Game designers: $73,864
Quality Assurance: $54,833

Check the link below.

http://www.payscale.com/research/US/Job=Video_Game_Designer/Salary