Regardless of whether the OP is overestimating himself/herself, the reality, based on high income parents who will not pay, is that s/he must find a school where s/he can get a large enough merit scholarship*, or not go to a four year college at all. So the targets (GPA, PSAT for NM, SAT/ACT) are roughly known, at least.
*Or otherwise free or low cost like military service academies, ROTC scholarships, or athletic scholarships, but those are highly selective, perhaps more so than many other large enough merit scholarships, even if the OP is interested in them.