system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How can Steam sell games so cheap?
gpt
In a brick and mortar store, there is only so much shelf space.  Most of it is going to be taken up by $50-$60 new releases with a high profit margin.  They just can't make enough money to keep the lights on selling $20 games.

Steam doesn't have this problem, their shelf space is unlimited and it cost them almost nothing per unit to send them out.  So if they want to sell some 4 year old block buster for $10, that's almost pure profit for them and the publisher.