I was wondering...
Do Aperture test subjects get paid? Most who I have asked say no...
Yes, they were paid... but then GLaDOS came in
Listen to Cave's lines in Portal 2.
i think they were payed up to the point that glados assumed control and changed all the rules. i speculate that on the papers subjects had to fill out for testing, there was a question where they had the option to name an additional prize for completing the test. i'm guessing that some time before portal 1, glados abducted chell for testing and filled out the form for her using the defaults, which explains why chell was supposed to get a chocolate cake, likely the default for the optional prize. it also explains the crazy stuff glados keeps saying is in chell's personnel file, because the file is likely all based on defaults meant as placeholders on actual information. it's fun to speculate about aperture science's system. 
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Im blue, a Clean Christian Furry with Autism.
1950s (Repulsion gel era): Test subjects donate to charity (Aperture is very wealthy).
1970s (Propulsion gel era): Test subjects paid $60 (If they fill out a form legibly) and an additional $60 if they volenteer to be dissected (then put back together).
1980s (Conversion gel era): Employees test (Assuming they don't get extra pay).
GLaDOS: Don't think she'd pay subjects anything.
See "signage/underground_70s_sign_2", "signage/underground_80s_volunteer" and "signage/underground_warning_whitegel".
Cave line 1, Cave line 2, Cave line 3
In the Lab Rat comic some of Chell's paperwork is visible, since Doug took it.
[spoiler]- BEE2 Addons | (BEE2)
- Hammer Addons
Maps:
- Crushed Gel
- Gel is Not Always Helpful[/spoiler]