Any place where prices are negotiated or offered individually (e.g. real estate, motor vehicles) is a place where price discrimination occurs. However, the magnitude is often greatest in colleges, where prices may vary from 5% to 100% of the college’s list price (it is not too common to buy real estate or motor vehicles for 5% of the list price).
It looks like many colleges want to keep the awarding of merit scholarships opaque, so that they can change the number and amount awarded on the fly without having made promises that would be inconvenient to keep if the college’s budget does not allow it this year (perhaps because of greater need-based financial aid expense or other non-financial-aid expense). They also want to favor admits who are particularly desired and who are likely to have other attractive admissions, and these factors are often determined subjectively on the fly.