Things you spend money on while making 1 screen
1.film or paper your image in on
2. electricity for the bright light that is required to burn the image onto the screen
3. emulsion that is on your screen
4. tape that is used to go on the screen anywhere the emulsion may not have covered
5. water must be used to wash the screen before and after printing (water bill)
6. materials that go into reclaiming the screen after the job is done and the materials you may use to get rid of excess ink that is still in the screen after the job is done.
7. pay an employee to do this for you or time is money and you will have to do all of this yourself
You can use a screen over and over and over again but there is alot that goes into making one screen; time+materials=money whether you are making it or spending it

Hope this helps you to understand what goes into making a screen

I may have left out some steps too so others are free to jump in
