The NSA didn't cut those companies a check. As the slides very clearly show, PRISM is an integration program between the NSA and the FBI to consume the data that the FBI already gets from issuing wiretap requests for specific users.
But this is about Mozilla, which is not all like the other big tech companies. They've definitely made some mistakes but I'd pause for a long time before accusing them of malice at that level.
How are they different?
Many contributors are volunteer, not under mozilla payroll. I doubt they would stay quiet if they notice something like this happen.