It is relatively fair and by no means vetoable. Jones has sucked, but he has not lost his job yet, and a closer for a good team always has value. Lee is perhaps the streakiest hitter in MLB and will not hit like this all year. You can't penalize someone for selling high.
There is actually not a ton of difference between Lee and Burrell over 162 games. Lee will steal 10 bases and have a slightly higher BA and a couple of more Rs, but that is about it. RBIs and HRs are more or less a wash. Greene is worthless, so the question is: Is Todd Jones worth 10 SBs, a couple of Rs and maybe .001 in BA in the final standings? A lot of people would take the saves and say "yes".