Rodon was the only free agent pitcher this offseason and there were none last offseason. As a matter of fact, there have only been 3 free agent pitchers in the last 4 years to receive a contract of more than 5 years.
If the Cardinals would have signed DeGrom and made a trade for another quality SP, they could have traded a little salary while receiving a rotation upgrade without sacrificing too much, in all likelihood. Overall, the team salary would have went up.