When DVDs were new, a new release around me would often be more like $25-30. Boxed sets would often be $50+. Of late 90s/early 2000's money, so $30 back then is like $55+ today.
I own lots of DVD's. DVD day was my jam. Most new releases were 20. Sometimes if they were some sort of special collectors edition they would be 25. Then usually after a few months on the shelf they would come down to 15-18. After that the bargain bin. Bluray/HD started around 25-30 when they came out. Box sets were usually like you say 50+ some as much as 200.
How many of those dvds are too scratched though? That would be like half of the blockbuster dvds we’d get. Even tried playing a dvd again at my folks and hit an unskippable scratch I couldn’t even see on the disc.