system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do movies filled with A-List Actors such as the Expendables 3 and Movie 43 manage to pack so many actors while keeping relatively low budgets?
gpt
Cameos. Get a star to spend one day on set and record a few scenes. Some even do cameos for free as they as good promotion for the actor. There will be more factors at play and other reasons which hopefully others will be able to explain in more detail, but this is definitely one reason.  
Also for Die Hard they HAD to get Bruce, which means he can demand loony money.