Yes, it was a factor in his sentencing (the whole debate about whether or not it was charged was because it was included as a factor in the proposed calculation for sentencing.)
Its not "murder", its "soliciting murder in the furtherance of a conspiracy". Which is not a separate crime, but manner in which the crime of conspiracy is achieved.
(Soliciting murder itself can be charged as a crime, and Ulbricht is charged with that, too, though those charges were not tried with these charges.)