Harper turned down a 12-year, $310-million offer from the Giants, according to Alex Pavlovic of NBC Sports Bay Area.
But Pavlovic notes San Francisco's offer would have had to significantly exceed the total monetary value of the Phillies' deal because of state taxes in California.
After missing the postseason in each of the last two years, the Giants were a late entrant in the Harper sweepstakes. Team CEO Larry Baer and president of baseball operations Farhan Zaidi reportedly met with Harper in Las Vegas for the second time in a matter of weeks on Tuesday in an effort to land the former NL MVP.
The Giants enter the season with underwhelming outfield options for a team hoping to compete for a playoff spot. San Francisco's outfielders finished 28th in the majors in WAR last season and the front office added only Gerardo Parra, Craig Gentry, and Cameron Maybin on non-guaranteed deals this winter.
Should they wish to pursue additional help, the Giants have room under the luxury-tax threshold with $171.6 million in salary currently committed to the 2019 roster, according to Cot's Baseball Contracts.