system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do they sell blu-ray and dvd in the same pack?

I'm looking to buy a series but the only option is to buy a blu-ray and dvd combo pack.  I haven't got a blu-ray player so I won't buy it but I got me thinking, other than a marketing ploy us there a reason why they sell both together? . 
I mean the blu-ray has everything the dvd has so why have both in the same pack?
gpt
Making the actual discs is very very cheap. It's so cheap that it's cheaper to just pack and sell both the BR and the DVD discs together, rather than making two separate production and distribution lines for the BR and the DVD.