Dude! It can't be THAT bad!
YARTS Yosemite to Merced is $25, and Amtrak Merced to L.A. is $58.
Visalia to Sequoia shuttle is $15.
Granted, there may be an overnight required someplace, which could make it far more expensive, but at least there IS transportation available.
Calif is a biig state, and it is a long way from the Central Valley to the sweet spots in the National Parks.