Onyemata is projected to get anywhere from $7-10m a year depending on the source, but the general consensus is that the market for interior DL will explode this year because DT is a need everywhere.
With Carr it would have been difficult if not impossible to re-sign him, much less to replace those 3000 total lost snaps. Onyemata had close to 700, we need 2300 more even if we do keep him. I think edge might be ok with Cam/Granderson/Turner, but our only DT under contract has 27 career NFL snaps.