Knott's Berry Farm charges $100 at their gate, though you can usually get passes for $75 online if you buy in advance. Their season passes cost $140.
Six Flags Magic Mountain charges $120 at their gate, but offers tickets for under $70 online. Their annual pass is about $150 ($20 fee plus $11/month for 12 months). The one benefit of this pass is it is valid at ALL Six Flags parks.
Cedar Point is $85 at their gate, but offers tickets for around $50 online. Their annual pass is only $110 with an option to get their "Gold" pass for $140 which includes both of their parks, a parking pass, and other perks.
Lagoon is $98 at their gate. Discount tickets are typically hard to find. Their annual pass is $208 (though it's only $190 if you buy before June, and $160 if you buy in November during their Black Friday sale).
I would argue that Lagoon's gate prices are pretty fair - BUT unlike other parks discount passes aren't as readily accessible online. While other parks advertise around $100/day gate prices, they also advertise significant discounts with online pricing. Add to it the relatively expensive pricing for their annual pass. Think about this - an annual pass that is good at all Six Flags Theme Parks and Water Parks is only $150. Lagoon charges $200 for their pass. That is a bit overpriced IMO.