According to Old Cars Magazine. In addition to their bi-monthly Old Cars Price Guide, they put out a book every year called "Collector Car Price Guide," and in an article about the upcoming 2020 issue in the most recent (September 12) issue of the magazine, they said this Later on in the same issue of the magazine, in their "Auction Express" column, they mention the sale at the July Mecum auction in Denver of a 1976 Buick Estate Wagon. Their price guide condition 4 basically says "runs and drives but needs full restoration." Condition 3 is "car show" condition, or a "20-footer." Anyway, the most recent edition of the OCPG to feature values for 1976 model year cars is the May/June 2019 issue, and it places the value of a #4 condition 1976 Buick Estate Wagon at about $2,500. The sale price of $7,700 for the car above would seem to support the contention that wagon prices are rising.