Try Big Basin. It is a state park, filled with redwoods.
I don't know the rate, probably $15-20$  < total guess,
it's been about a year since I've been there.  It is 
located about 25? miles from Santa Cruz.  To get there,
the easy way is to take Hwy 9 North from Santa Cruz to 236
west which will take you directly to the ranger station.  If
you feel adventerous, you can take Hwy 1 along the ocean,
and then take some park road East into Big Basin - I haven't
ever gone this way, but it can be done.  There are also
some State beaches along the way on 1 that I hear the CHP
will look the other way if you camp there, but you are on 
your own there.

Good luck - enjoy...

Pat Wheaton
Mt. View CA