My twins were in a fairly similar position three years ago, not wanting to pay much more than full pay UC costs (though with slightly higher stats: 1540 SAT for S18 and 35 ACT for D18).
S18 applied widely for merit at T50-T100 privates and OOS publics but couldn’t get below about $45K per year, the best value by far was the UCs and he loves it at UCLA (he got a small amount of merit there too but it wasn’t the deciding factor). The only college that would definitely have offered better value for money was Oxford and unfortunately he wasn’t offered a place after interview.
D18 applied to a range of schools with strong dance programs, many of which were T100-T200 OOS publics. She had better merit offers and ended up with a full ride OOS, but we attributed a lot of that success to her unusual combination of very strong academics and applying for audition-based programs. I doubt she would have been so successful applying for a more conventional academic major. For example she was offered an OOS tuition waiver at UT Austin of which there are only a literal handful available each year and got Regents at UCSB and UCI. It’s important to take that into account when thinking about merit possibilities for a kid (like her brother) with no real hooks.
There’s no question that D18 has a better deal than S18 but if she had been applying for a conventional academic major then I’m pretty sure she wouldn’t even have applied to her current school and would instead have gone to UCLA with her brother (both of them got into UCB and UCLA, but Berkeley is too close to home). Most of her classmates with the same scholarship were either in-state or were explicitly merit hunting because they couldn’t afford the cost of their in-state flagship. You are fortunate to have great affordable in-state options so can apply to a few lottery ticket scholarships, but the chances of winning enough to get better value for money than the UCs is not high.