We spend July and August summer in that area every year, and the prices are high everywhere there. Location, location, location.
We stay at Marina Dunes, which is much closer to Monterey. Marina Dunes is $65 a night or $1200 a month for the big rig sites, which are very large and private.
The only other choices are Laguna Seca, which has no sewer hookups, a KOA further up the coast in Santa Cruz, a tiny park in Carmel Valley where you are on top of each other, and away from the nice coastal weather, or the Fairgrounds. We have stayed at the fairgrounds for a few days each year at the beginning or end of the trip, but it is just a parking lot next to the horse corral, and it is closed for special events most of the time in the summer.