Thus ends the brief stay of Bobby Jenks filling out a Boston Red Sox uniform.  That breaks down to $631,579 each time he waddled in from the bullpen, $765,795 per inning worked, and $40,816 per each of the 294 pitches he threw. His per pitch pay rate was greater than the average income per person in 18 of the 50 states in The United States of America. 

That said, that is not even close to the worst use of $12M in baseball. That honor belongs to the Tampa Bay Devil Rays in 2000.

Prior to that season, owner Vince Naimoli provided General Manager Chuck LaMar with money to attract free agents to the Tampa Bay area and LaMar went shopping in earnest. He first tried signing Aaron Sele, but ended up signing Juan Guzman to a two-year deal for $12M. He was coming off a season in which he made 33 starts and threw 200 innings while pitching for both Baltimore and Cincinnati. Guzman took to the mound on the fifth game of that season for the Devil Rays' home opener after the team had split a series at Minnesota to start the season. Tropicana Field was packed with 40,329 fans who'd come to see the new names on the Devil Rays and their big free agent signing on the mound. Fans that were late getting into the game due to traffic or were in lines at the concession stand never got to see Guzman pitch as he left the game with an injured shoulder on his 55th pitch of the game while trying to get out of the second inning and never again threw a major-league pitch. 

The total bill for Juan Guzman's time with the Devil Rays: $12,000,000 per appearance, $7,185,628 per inning worked, and $218,189 per pitch thrown.