With the recent terminations of individuals like Tillerson and McMaster, I was wondering if this is costing taxpayers money. Do fired officials get a pension, severance, or other financial compensation? Would it be determined by law or case-by-case negotiation?
Cabinet members follow rules similar to those of the VP and congress members:
As with salaries, the rules governing the retirement benefits of the Vice President, Cabinet members, members of Congress and other federal officials are different than those that apply to the President, with benefits laid-out in the rules of the Federal Employees Retirement System (FERS) and the Civil Service Retirement System (CSRS). Thus, their retirement benefits (including pensions) will vary from individual to individual, depending on factors such as years of service.
This document from the Senate has a bit more details:
Under both CSRS and FERS, Members of Congress are eligible for a pension at age 62 if they have completed at least five years of service. Members are eligible for a pension at age 50 if they have completed 20 years of service, or at any age after completing 25 years of service. The amount of the pension depends on years of service and the average of the highest three years of salary. By law, the starting amount of a Member’s retirement annuity may not exceed 80% of his or her final salary.
Put another way, yes, their pensions can potentially cost money, provided they're entitled to having a pension to begin with.
One question worth asking in passing, is whether Trump's billionaire cabinet members really cared much about their compensation. The $210k as Executive Schedule I that Tillerson got is chump change compared to the generous retirement package Exxon gave him.