Dean Jones says:

"OK, let's discuss the possibility of your having a paid research assistant for a longer period.  We are looking to promote our university as providing both a teaching-oriented and research-oriented education.

If we grant you funding for a multi-year research assistantship, do you think you would be willing to also supervise graduate and undergraduate "independent study" student research projects in your field of research?  Say, six students per year? 

I'll agree to "split the difference" and provide funding for two years if you will agree to supervise six independent study projects per year." 

Your response:

1.  "Certainly.  That sounds fair.  I agree."

2.  "I think you are 'splitting the difference' on the years of funding, but not on the added requirement for supervising student research.  Is that really fair?  After all, you are asking me to do a lot of extra work!

Here's my counter-offer:  I will agree to supervise six students per year ONLY if you agree to provide funding for a paid research assistant for three years."